The Big Keto Mistake... How Eat For Longevity.

This is going to be a long video, and I say that because there is more confusion around the ketogenic diet than almost any other topic I get asked about. And let me just say that keto, despite all of its complexity and controversy, is actually pointing us in exactly the right direction. And I say that because the underlying driver of the chronic diseases that kill most people, which is cardiovascular disease, and certain cancers, and dementia, and type 2 diabetes, is to a very significant degree metabolic dysfunction.

Specifically, a problem called insulin resistance, which we'll come back to in a lot more detail quite often in this video. And the core idea behind ketogenic thinking is that if we can get our bodies burning fat rather than burning glucose, we can reverse or prevent all of that metabolic dysfunction. And that is a pretty sound way of thinking, to be honest. Thinking about how your body uses fuel and whether you're making it work harder than it needs to is one of the most important questions you can ask about your long-term health.

Now, the question I want to answer in this video is not whether the logic of keto is good. The logic is quite good. The question is, what is the best practical approach to that logic for the majority of people? And that's the important part for most people because, you know, the average person watching these videos doesn't know where to start with their health. That's the impression I get when I read through the comments. So, for the average person who isn't already optimizing most parts of their health, what is the best approach? Is it full keto? Is it just cutting sugars and refined carbohydrates? Is it cycling in and out of keto? And what does the evidence actually say about what works, what is sustainable, and what could cause harm if it's done wrong?

And I want to go through the actual evidence from these large meta-analyses and long-term population studies, all the way down to the smaller randomized control trials, and even some animal research, because it's quite interesting, to be honest. And I want to be upfront about what each piece of evidence can and cannot tell us. Now, if you want to skip to my final recommendations at the end of the video, then you can use the timestamps to jump around the video. I always put those in the descriptions of these videos, but I would encourage you to stay for a bit of the physiology as well, because understanding how the body actually handles fuel is what makes the conclusion make sense. Without it, the answer might just sound like another piece of dietary advice without any context. So, even if you don't get through all of this video in one go, maybe just pause it and come back to it. Having a bit of an understanding about glucose and fats and insulin resistance and the best foods for us, really, really helps if you're wanting to become healthy.

Before any of that, though, we need to make sure we're talking about the same thing, because half of the confusion around keto actually comes from people using the word keto but meaning something else. So, let's clarify what we're actually talking about here. So, the first section of this video is all about what keto actually is, and what is the physiology? What is the biology around keto? So, the first question is, what does the body actually run on? At the most basic level, your body runs on two main fuel sources, which are glucose and fat. And under normal circumstances, glucose comes first.

Glucose is a simple sugar, the molecule that your body extracts when it breaks down carbohydrates. It's pretty simple stuff. So, when you eat bread, or pasta, or rice, or oats, or fruits, or potatoes, or any other carbohydrate-containing food, your digestive system breaks it all down into glucose, which gets absorbed into your bloodstream and transported to your cells as energy. So, your brain, and your muscles, your heart, all of them use glucose. It is the default fuel.

Now, here's something that a lot of people don't really know. Not all carbohydrates actually taste sweet, even though they all eventually become glucose in the body. Well, why is that? Why is it that fruit and table sugar and juice taste sweet, but potatoes and bread don't taste sweet, but they all get broken down into glucose in the body? Why does that happen? Well, the answer comes down to the type of sugar molecule involved and how it interacts with your taste buds. So, table sugar, which is sucrose, is actually made out of two molecules joined together, which is glucose and fructose. Now, fructose is the sweetest naturally occurring sugar we know of, significantly sweeter than glucose itself. When sucrose sits on your tongue, it activates the sweet taste receptors immediately and powerfully, partly because fructose binds to those receptors more effectively than glucose does. Now, fruit mostly contains fructose, which is why it tastes sweet. Honey is rich in fructose, so the same reason.

Now, starchy foods like bread and oats and rice and potatoes are made of long chains of glucose molecules linked together, a structure that we call a polysaccharide. Now, these chains are too long to fit on the sweet taste receptors on your tongue. Your taste buds simply cannot read them the way that they read fructose or sucrose. So, they do not register as sweet, even though once digested and broken down by enzymes in your gut, they release exactly the same glucose molecules into your bloodstream. The sweetness here is a property of the shape and size of the molecule, not how much glucose eventually ends up in your blood. This is why people get confused about how things that don't taste sweet, like bread or potatoes, can cause just as much damage as something like fruit or table sugar. Well, that's partly why.

So, if glucose is your default fuel, what happens when there's too much of it, when you eat too much carbohydrates? Well, your body cannot store unlimited glucose in your blood. Blood sugar levels are very tightly regulated, because if they go too high or too low for too long, it can cause serious damage to your organs, and hypoglycemia can actually kill you. And high blood sugar, the kind that's sustained over months and years, which describes most adults in the Western world, to be honest, is physically damaging to the walls of your blood vessels. So, glucose at high concentrations acts almost like a corrosive agent on the delicate inner lining of those arteries and capillaries. It triggers a process called glycation, where glucose molecules literally stick to proteins in the vessel walls and change their structure, making them stiff and dysfunctional. They don't work as well because glucose has changed them. It drives something called oxidative stress, which is a kind of cellular rust, and it also triggers chronic inflammation inside the blood vessels themselves. So, over years, this really does damage the tiny blood vessels supplying the kidneys, and the back of your eyes, the retina, and it can cause blindness and neuropathy in your feet. And importantly, it also accelerates the stiffening of your coronary arteries feeding your heart, and the carotid arteries feeding your brain. It dramatically increases your risk of heart attack and stroke over this sort of long time span. This is why chronically high blood glucose kills people. It is a very serious risk. It is a slow, progressive destruction of the body's most delicate plumbing, playing out over years and decades.

And as we just said, a low blood sugar is also super, super dangerous, hypoglycemia. And the reason is that the brain depends almost entirely on a continuous supply of sugar or fuel. And if your blood sugar drops too far, your brain function deteriorates rapidly. So, within a few minutes, you get confusion and seizures, and you become unconscious. And if that's not treated, then people die. And I've seen this a handful of times in my career so far. So, people are found on the street, they are hypoglycemic, and we have to inject intravenous glucose just to give the heart and the brain energy to to survive, because if they don't get the the raw fuel that they need to convert into energy, then those organs will die, and that patient won't survive. This is why the body regulates blood glucose so tightly, because the consequences of getting it wrong in either direction are severe.

So, anyway, a bit of a tangent there, but excess glucose gets converted into a storage form called glycogen. So, if you eat more glucose than your body needs at that moment, it gets stored as glycogen, which is then packaged into two places: your liver and your muscle. So, think of this less like a reserve fuel tank that kicks in when the main tank runs dry, and more like a very, very short-term buffer, a small, rapidly accessible supply that bridges the gap between your last meal and your next one, or that gets your muscles through a burst of intense exercise. And the thing is, this is not a large reserve. Your liver holds around 100 grams of glycogen. That's it. Your muscles hold between 400 and 500 grams between them, you know, depending on how big you are. So, in total, that is roughly 2,000 calories worth of glycogen storage, enough to get you through a day of normal activity or a couple of hours of really intense exercise. Once those stores are full, any extra glucose that comes in gets converted to fat and stored in the body's long-term fat reserves. And yes, that fat is stored primarily as triglycerides, which are the body's main form of long-term energy storage. Now, a triglyceride is basically three fatty acids attached to a glycerol backbone, and that is what accumulates in your fat cells, in your liver when there is too much of it, and in the visceral fat around your organs. So, when people talk about fat, really, they're talking about triglycerides.

Now, before we go any further, let's talk about insulin. What is insulin and why does it matter so much? So, insulin is a hormone produced by your pancreas, here, a gland that sits behind your stomach at the top of your abdomen. So, think of insulin like a key, and your cells throughout your entire body as rooms with locked doors. So, glucose is in the bloodstream and needs to get inside your cells to be used as fuel. Insulin is what opens the door in every cell. When your blood glucose rises after a meal, your pancreas detects that and releases insulin, which travels through the blood and binds to receptors on the surface of your cells throughout your body, effectively unlocking them so glucose can flow in.

Now, in a healthy person, that system works really well. You eat, and your blood sugar rises, insulin is released, glucose enters your cells, and then your blood sugar or blood glucose comes down, and then your insulin level then falls. So, it's really clean and efficient and rhythmic as well. But what happens when this system starts to break down? Well, this is where metabolic dysfunction actually begins. So, when your blood sugar is chronically elevated over months or years because of a diet high in refined sugars or processed food and refined carbohydrates, the pancreas has to keep pumping out insulin to manage it. And over time, with constant high levels of insulin in the system, the cells start to become less sensitive to it. They start to become resistant to insulin. So, the key still works, but the lock is getting a bit stiff. The pancreas has to produce more and more insulin to achieve the same effect. It's a bit like when somebody is walking outside of our house, our dog Mango will hear it and he'll bark. He'll go crazy. But if somebody is walking repeatedly outside, after a while, he'll become immune to that sound. And it's only after a long period of no people outside where it's silent, if you then hear somebody again, you'll then start barking again. It's a bit like insulin there. So, if glucose is there all the time, insulin stops responding as well. So, the pancreas has to release more insulin, more of that less effective insulin, just to bring glucose down. I hope that makes sense.

And eventually, if all of that continues unchecked, if nothing is ever done about it, the system will start to fail, your blood glucose will build up in the blood. And at that point, when your glucose then starts to rise, that is the point when we diagnose people with pre-diabetes or type 2 diabetes, if it's high enough. Clearly, if you've been listening to what I've said, insulin resistance, the problem, the metabolic dysfunction, has been happening years before that diagnosis is made. This is why insulin resistance is at the heart of so many chronic diseases, because it's not just about blood sugar. Chronically elevated insulin levels are linked to inflammation, to increased fat storage, because insulin is a storage hormone, particularly in the liver and around the organs, and also elevated triglycerides, and to a cascade of effects that increase the risk of cardiovascular disease, certain cancers, and dementia. And understanding that entire loop is arguably the most important thing that you can do for your long-term health.

And this is precisely where the logic of reducing carbohydrates, whether through keto or a less extreme approach, becomes so powerful. When you reduce the amount of carbohydrates coming in, particularly the refined sugars and processed carbs, and basically what that means is without the fiber that causes the sharpest blood glucose spikes, you reduce how often and how hard the pancreas has to pump out insulin. Insulin levels then spend more time at baseline. The cells get a chance to recover their sensitivity. The lock starts to work properly again. Visceral fat and your liver fat, which are both drivers and consequences of insulin resistance, begin to reduce. And as that vicious cycle starts to unwind, the downstream risks start falling as well. So, your blood pressure will improve, your inflammatory levels will fall, your triglycerides will come down, your cardiovascular risk decreases. This is why getting control of your carbohydrate quality is not just about weight loss. It is about interrupting the metabolic chain of events that leads to the diseases most likely to kill you. And top of that list is cardiovascular disease.

Okay. So, what is the counterpart to insulin? What's the opposite of insulin? What happens when the body needs to release energy rather than store it, which is what insulin does? This is where glucagon comes in. So, if insulin is the store energy signal, glucagon is the release energy signal. When blood glucose drops, either because you've not eaten for a few hours or because you're exercising really hard, the pancreas releases another hormone called glucagon into the bloodstream. And glucagon is actually a drug that we use in emergency medicine. So, when a patient comes in with a dangerously low blood sugar, what we call a hypoglycemic emergency, one of the treatments we reach for is an injection of glucagon. We can give it into the muscle, either the upper arm or the thigh or the buttock. And within about 10 minutes, your blood sugar will start to rise. And what it does is travel to the liver and tell it, there is an emergency happening. Release all of your glycogen stores now. So, the liver breaks down its glycogen back into glucose, because glycogen is just a stored form of glucose, sort of clumped together, which then rapidly raises your blood sugar.

And this is a critical point here. The glucagon injection only works if the liver has glycogen to release. So, if somebody has been starving or if they've been on a very prolonged fast, the liver glycogen will already be depleted, and the glucagon injection will not work. So, in that situation, we have to give glucose directly into a vein instead. So, if we have a patient that comes in who is hypoglycemic and they look really skinny, glucagon probably isn't going to work. It is a small but very vivid illustration of how central glycogen storage is to keeping us alive. Now, glucagon acts primarily on the liver. It is the liver's glycogen that gets released into the blood. Muscle glycogen is used locally by the muscles themselves during exercise. It does not get released into the bloodstream for the rest of the body.

So, what is the actual order in which your body burns fuel? Well, the first fuel that it uses first is glucose that is directly available from what you've just eaten. The second one, once that glucose runs short, is your glycogen. So, glucagon kicks in, and the liver releases its stored glycogen. The third one, once those glycogen stores are depleted, which takes somewhere between 12 and 24 hours of fasting, or much faster during intense exercise, the body shifts to burning fat and producing ketones. This is the sequence, and it's important because it tells us that ketosis doesn't happen instantly. It requires you to work through those first two stages first. So, your glucose and your glycogen, which is just stored glucose.

Now, an interesting question here is, if glycogen is just chains of glucose, and starch is just chains of glucose, then what is actually the difference between them? So, starch, which is the storage form in plants, has a relatively simple branching structure with branch points occurring roughly every sort of 25 to 30 glucose units. Glycogen, which is the storage form in animals, including humans, is far more densely branched, with a new branch point roughly every 8 or 12 glucose units. So, more branch points means more places where enzymes can attack simultaneously and release glucose rapidly. So, glycogen is designed, or we've evolved with glycogen, for speed. Exactly what your liver needs when blood sugar drops in an emergency. Starch in a potato releases glucose much more slowly as you digest it. So, it's the same building block, but a very different structure with a very different behavior.

Okay. So, let's talk about ketosis then. So, what actually happens when the body runs out of glucose and glycogen and shifts into fat burning mode? So, at this point, the liver starts breaking down fatty acids in the liver through a process called beta oxidation. And as a byproduct, it produces three types of ketone bodies. The first one is beta-hydroxybutyrate. Then you've got acetoacetate, and then finally one called acetone. Now, two of these, beta-hydroxybutyrate and acetoacetate, travel through the bloodstream and get used as fuel by the brain, and your heart, and your muscles. The third one, called acetone, is a bit different. Unlike the other two, the body can't actually mobilize acetone as fuel. It is a waste product that gets exhaled through the lungs, and it smells a bit funny. This is why people in ketosis often have a bit of a fruity smell on their breath. Some people say it smells like pear drops or nail polish remover. So, if you've ever been around somebody doing extended fasting or a strict keto diet and noticed a slightly sweet quality to their breath, then that is the acetone you are detecting.

Now, in emergency medicine, that fruity smell is something that we take really seriously. In a patient with type 1 diabetes who is not managing their insulin properly, it can be a sign of a life-threatening emergency called DKA, diabetic ketoacidosis. In DKA, ketone production has gone completely out of control because in type 1 diabetes, or in these emergencies, there is no insulin to be able to use the glucose. So, the body has to mobilize and break down fat and produce ketones to literally survive. So, we smell the same thing, that pear drop, nail polish remover sort of smell. Clearly, these two are completely different things. The fact that we can smell a bit of a fruity smell in ketosis in otherwise healthy people doesn't mean it's dangerous. But just a bit of a distinction there to mention.

But what about the brain then? Can the brain actually run on ketones, and does it function as well compared to when it uses glucose? So, the brain cannot use fat directly. Fat molecules cannot cross what we call the blood-brain barrier, which is that protective membrane that strictly controls what enters the brain. So, your brain is dependent on either glucose or ketones. Now, ketones can fuel roughly 70 to 75% of the brain's energy needs. The remaining 25 to 30% still requires glucose. But in full ketosis, where does that residual glucose actually come from if you're not eating carbohydrates? Well, your liver makes it through a process called gluconeogenesis, which literally means making new glucose. The liver can manufacture glucose from amino acids, which are the building blocks of proteins, and from glycerol, which is a component of fat molecules. Now, this process does require a good amount of protein intake. So, a poorly formulated keto diet where protein is too low can compromise it. This is a pretty bad habit to build. If you're in keto, then you've got to have enough protein. So, even without eating a single gram of carbohydrate, as long as you're eating enough protein, your brain gets the small amount of glucose it needs through this internal manufacturing process. You don't need to eat carbohydrates for your brain to function. Both ketones and glucose produce ATP, which is adenosine triphosphate, which is the fundamental energy currency that every single cell uses. So, the end result in terms of powering the brain is pretty similar.

Now, some research suggests that ketones may produce slightly less oxidative stress during energy metabolism, a kind of cleaner burn, if you like, which has driven a lot of interest in their potential protective role in diseases like Alzheimer's, where the brain's ability to use glucose seems to decline. But for a healthy person with a normally functioning brain, the practical difference day-to-day isn't dramatic. What the research does support is the concept of metabolic flexibility. And I've mentioned this a few times in other videos, the ability of the body to switch very efficiently between using glucose and ketones depending on what is available. So, a body that can do this is more resilient and adaptable than one locked into either fuel exclusively. And so, every day, like I do, if you're fasting overnight by 14 hours, so you're having your last meal at 6:00 p.m. and your breakfast at 8:00 a.m., that's just about long enough for your body to start burning some fat to produce ketones, because clearly you're not eating for 14 hours. So, every single day, my body has a bit of practice to produce ketones. So, I'm hoping my metabolic flexibility will be quite good. The goal really isn't to permanently eliminate carbohydrates and just live off ketones. The goal is to avoid the situation where the body is so flooded with glucose and insulin every day that it never gets a chance to burn any fat at all.

But just say, for instance, that you are in full ketosis. You never eat any carbohydrates at all. So, you're always using your fat to produce energy. Will you ever run out of fat to burn? Well, in practice, for virtually every single person watching this video, the answer is no. Even a relatively lean person carries enough stored fat to provide tens of thousands of calories for fuel. Somebody who's overweight may have hundreds of thousands of calories in fat storage, but really, you're going to be replenishing that fat with the fat that you eat and the protein as well. A more realistic concern is not running out of fat. It is actually running out of micronutrients and electrolytes, like the vitamins and the minerals and the fiber that whole plant foods provide, and that a strict ketogenic diet tends to exclude.

So, after all of that, what does a true ketogenic diet actually look like in practice? Well, a true keto diet means getting around 70 to 75% of your total calories from fat, around 20% from protein, and no more than five to 10% from carbohydrates. Because, let's be honest, it is pretty difficult to eliminate carbs entirely. Now, in practical gram terms, that usually means staying under 20 to 50 grams of carbs per day. Now, to put that into perspective, what that means is, you know, a single medium banana contains around 27 grams of carbohydrates. A slice of brown bread contains around 15 grams. A portion of lentils, which we always recommend to eat, is around 40 grams. So, already that's something pretty significant there. If you're trying to cut out carbs, then you're going to cut out a lot of the healthy stuff that we recommend to eat. A handful of oats is around 30 grams.

So, to maintain full nutritional ketosis, you would need to eliminate pretty much all bread, all pasta, rice, oats, and grains of any kind. So, all legumes, so that's lentils and chickpeas and kidney beans and black beans, peas. Most fruit as well, most root veg, that's potatoes and sweet potatoes and parsnips and carrots and yams as well. Most dairy as well, beyond cheese and cream. So, what remains really is meat and poultry and fish, eggs, cheese, cream, butter, olive oil, avocado, and very small amounts of leafy green vegetables.

And here's something that is absolutely underappreciated in this whole keto conversation. I don't hear many people talking about this, and it directly affects whether this is a sensible long-term approach. And I've just touched on this at the beginning of this section, but let's go into this in a bit more detail. So, many of the foods that you eliminate on a full keto diet are not just convenient sources of carbohydrate. They are among the most health-protective foods that we know of. So, as I mentioned, legumes, so lentils and chickpeas and beans, are extraordinarily rich in fiber, in plant protein, and also polyphenols. They've been consistently linked in large studies to reduced cardiovascular risk and reduced all-cause mortality, death from any cause. Whole grains provide not just fiber, but also B vitamins as well, and magnesium, and prebiotic compounds that feed your gut bacteria. Fruit as well. They contain vitamin C and potassium and antioxidants and fiber as well. So, the carbohydrates in these foods really isn't the problem. These are some of the most nutrient-dense foods on the planet. And we'll come back to this tension between full ketosis and gut health in a bit more detail when we get to the evidence on the microbiome.

Now, crucially, most people, from what I can gather, who say they are doing keto are not doing any of that. They've cut out biscuits and cakes and soft drinks and white bread, and all of that is great, but that is not keto. That is simply reducing added sugar and refined carbohydrates. And as we'll see as we get into the research, those two different approaches, so full nutritional ketosis versus simply cutting out added sugar and refined carbs, produce very different results in the body.

So, that is section one finished. We've talked about ketosis and the physiology. Now, in section two of this video, we need to talk about what the evidence actually says. So, we're going to go through four key areas of evidence. And we've got to be upfront about the limitations of each piece of research as we go along, because, well, that's how honest medicine is conducted. We've got to be honest about the strengths and weaknesses of each study. And that isn't really what a lot of people do on YouTube, from what I can gather. And I'm going to try and look at the whole body of evidence together in this video, not just the studies that favor one position or the other.

So, the first topic in this section is all about LDL cholesterol and APOB, which you may have heard of, and your cardiovascular risk. So, what does keto actually do to your heart disease risk? Well, let's start with the finding that I think carries the most long-term clinical weight, and this is the one that gets a lot of pushback from people. So, a 2024 randomized control trial from the University of Bath, published in Cell Reports Medicine, compared three groups over 12 weeks: a control diet, a low-sugar diet, and a full ketogenic diet. Now, let's be upfront about the sample size here. So, it involved 53 people. That is obviously a very small trial, and any single small trial needs to be interpreted very cautiously. But the Bath study is not the only evidence. Far from it.

Now, in terms of the results, both the keto group and the low-sugar group lost fat. The keto group lost an average of 2.9 kilos of fat, and the low-sugar group lost around 2.1 kilos. So, keto produced slightly more fat loss, but by less than 1 kilo over 3 months. But what happened to cholesterol over that time tells a very different story. So, the keto group saw a significant rise in something called LDL cholesterol and apolipoprotein B, known as apoB. But what actually is LDL cholesterol? And why does it matter here? Well, LDL cholesterol is what a lot of people call bad cholesterol, but "bad" is quite a big simplification. LDL cholesterol tells you the total amount of cholesterol carried inside LDL particles in your blood. What it doesn't tell you is how many LDL particles there are. So, think of it like this: Imagine you are measuring the total number of people in a fleet of buses. If there are 10 buses with six people in each one, the passenger count is 60. If there are 60 buses with one person in each one, the passenger count is also 60. So, the standard LDL cholesterol test would give you the same number in both cases.

Now, bear with me on this, but those 60 buses are fundamentally different from 10 buses, because each bus can crash into an artery wall independently, if that makes sense. So, apoB is the particle count. Apolipoprotein B is a protein that sits on the surface of each LDL particle, one per particle without any exception. So, if you measure apoB, you are measuring the actual number of LDL particles circulating in your blood, and it is the number of particles, not the volume of cholesterol they carry, that determines how much arterial damage is happening. Multiple major cardiology studies have shown that apoB is a much better predictor of cardiovascular events than LDL cholesterol alone, which is why many lipidologists now consider it to be the gold standard measurement. So, the Bath study, the study in this topic that we're talking about now, found that the keto group increased apoB significantly. The low-sugar group in the middle had no change in apoB at all. So, it suggests that the full keto group might have a big disadvantage.

Now, you might have seen people push back on that argument by saying that keto also raises HDL cholesterol, the so-called good cholesterol, and it also reduces your triglycerides, which are fats in the blood. Both of which are true. But when apoB goes up, that means more LDL particles are circulating, each one capable of embedding itself into the artery wall, which then triggers an inflammatory response and contributes to the plaque buildup that eventually causes a heart attack and stroke. A slight rise in HDL does not eliminate that risk, and triglyceride reductions are really beneficial, but they do not cancel out the particle count problem. So, what that's saying is that the rise in apoB from the full keto group isn't canceled out by the other good effects that the full keto sort of style brings.

And it's also worth acknowledging another genuine scientific debate here, which is that a subset of people, typically lean, highly active individuals, can show quite dramatic LDL rises on keto while other markers remain okay. Some people argue that this represents a benign redistribution of lipoproteins in people who are already metabolically healthy, rather than a straightforward increase in cardiovascular risk. It's really complicated to get your head around and argue this point. But what researchers call this is the lean mass hyper-responder phenomenon. And it is a legitimate area of ongoing research. And I'm not dismissing this, but it applies to a very specific subset of already healthy, highly active people. It is not a reason for the general population to dismiss the LDL and apoB findings.

And the thing is, we're not talking about dramatic changes over a 12-week period here. We're talking about relatively small changes. But the thing is, cardiovascular disease is a very slow game. It builds up over 30 or 40 or 50 years. So, a very small increase in apoB sustained over decades means marginally more LDL particles steadily depositing into the coronary artery walls year after year. At some point in that process, and it could just be one extra particle on one particular day, like the straw that broke the camel's back, it could mean that there was enough plaque to rupture, and a ruptured plaque is a heart attack. And this is exactly how people end up in the A&E at the age of 55 years old.

And the finding is not from one small study either. A 2024 meta-analysis pulled data from 27 randomized control trials involving over 1,200 people and found a very consistent, statistically significant rise in LDL cholesterol on a ketogenic diet. So, it's not just one small study. This is a big meta-analysis. And a separate umbrella review of meta-analyses, published in BMC Medicine in 2023, covered 17 meta-analyses and 68 randomized control trials and found that this increase in LDL cholesterol from keto was rated as high-quality evidence. And so, what that means is that that is the highest grade of evidence in the sort of GRADE system, and what we use for sort of standardizing the strength of medical evidence. Only four findings in that entire review reached the high-quality evidence status, and the LDL rise was one of them. And this finding is one of the most robustly replicated observations in the entire keto literature.

So, to summarize this entire point, full keto consistently raises LDL cholesterol and apoB across multiple large meta-analyses and randomized control trials. Now, as I said, these aren't big, dramatic changes, but if you compound these small changes over decades, what that means is that the very small increases in the number of LDL particles circulating in your blood could increase your risk of coronary artery disease. And really, the interesting thing here is that people who are doing keto are doing it because they want to be healthy and reduce their disease risk. But you can probably guarantee that most people on keto aren't aware of this pattern that is showing up in the research. So, if there was an approach that provided most of the metabolic benefits of keto without raising your LDL, and this study suggests that there is, then surely that is something to take seriously.

Now, the second topic is all about how your cells age and also something called senescent cells. So, what are senescent cells and why should anybody following a keto diet even care about them? So, a study published in 2024 found that mice, so yeah, not not the best research paper, but bear with me, mice on a long-term continuous ketogenic diet accumulated what are called senescent cells in multiple organs, particularly the heart and the kidneys. So, every day throughout your body, in normal physiology, cells accumulate damage from radiation, from free radicals, from normal metabolic stress, from the simple act of replicating their DNA. Cells damage and replace themselves all the time. Now, most damaged cells either repair themselves or self-destruct in a clean, controlled process called apoptosis, making way for healthy replacements. This is just normal physiology. But some damaged cells do neither of those things. Instead, they enter a state called senescence. They stop dividing, but they do not die. They just sit there in your tissues, permanently dysfunctional.

Now, is senescence always harmful? Well, no. In small amounts and short time frames, senescence could be, well, it actually is useful. It is part of how the body suppresses cancer and helps to heal your wounds. Think of it like a temporary quarantine. The damaged cells get frozen in place so they cannot multiply and potentially become cancerous, while the immune system is supposed to come along and then clear it out. Your immune system, which is your natural killer cells, your T cells, your macrophages, this is the normal waste collection service for these senescent cells. Now, in a young, healthy immune system, this clearance works really well. The problem, though, is accumulation. So, as we age, or when something accelerates the production of senescent cells beyond the immune system's ability to clear them, they begin to build up. And here's where the damage comes from. So, even though senescent cells are not multiplying, they're not exactly silent either. They continuously secrete a cocktail of inflammatory signals, like cytokines and enzymes and other molecules as well, into the surrounding tissues. Now, this chronic low-grade inflammation from accumulating senescent cells is thought to contribute to the tissue damage seen in many age-related diseases, including heart disease and kidney dysfunction, and arthritis, and neurodegeneration as well, and also cancer progression. Cellular senescence is one of the most recognized hallmarks of biological aging, and clearing these senescent cells is currently one of the most active areas of longevity research. There are loads more videos appearing on this topic on YouTube over the last few months.

What this study found was that a continuous ketogenic diet appeared to drive senescence through a specific molecular pathway involving a protein which many of you might have heard of called p53, which is a very well-known tumor suppressor that operates similarly in human cells, and that when activated beyond normal levels can push cells into the senescent state. Now, that diet appeared to trigger this pathway in heart and kidney tissue in particular. The critically important nuance here for this study is that mice on an intermittent ketogenic diet with planned breaks, instead of a continuous one, didn't show that same accumulation. These senescent cells appeared with continuous keto, but not with cycling in and out of keto.

Now, obviously, this was mouse data. Mice are not humans, and we've got to be honest about what that means. The metabolic rates of mice and their lifespans and their immune systems and their hormonal environment are very different to ours. So, a finding in a mouse study, all it does is raise a hypothesis. It doesn't prove the same thing happens in humans. And, you know, we shouldn't change a patient's diet based on what a mouse study says alone. But what it gives us is a biologically plausible signal. Plausible because the p53 pathway involved in that study operates similarly in human cells. And that warrants proper investigation in human trials. And just because this was a mouse study doesn't mean that we can ignore it completely. It is a reason for caution about very long-term continuous true ketogenic diets, particularly given the cardiovascular findings that we just discussed.

So, the third topic is all about your gut microbiome. So, what is the gut microbiome and what does a ketogenic diet actually do to it? Well, your gut contains approximately 38 trillion, with a T, bacteria. 38 trillion, more than you have human cells in your entire body. Now, these bacteria are not just passive hitchhikers. They form a very living ecosystem that plays a very active role in your health in ways that science is still sort of mapping out. We're still discovering new things here. What we do know is that these bacteria produce vitamins, particularly B vitamins and vitamin K. They also produce short-chain fatty acids from the fiber that you eat, which feed the lining of your gut and have anti-inflammatory effects that extend well beyond just your gut. They train your immune system as well. The gut wall is the largest immune surface in your body because it is sort of connected to the outside world from your mouth all the way through to your stomach and your intestines and your anus. It is communicating with the outside, and the bacteria living on this surface help your immune cells to learn what to attack and what to leave alone. So, a disrupted microbiome, where the wrong bacteria dominate and then beneficial bacteria are depleted, this has been associated with increased levels of inflammation, and increased susceptibility to infection, and inflammatory bowel disease as well, which is a huge important one, and metabolic dysfunction, and even problems with your mood through the gut-brain axis, which is like a two-way communication network between your gut and your brain. The other important point here is that your microbiome also feeds straight back into the insulin sensitivity story. So, short-chain fatty acids produced by beneficial gut bacteria improve how your cells respond to insulin. And when those bacteria decline, that protective effect declines with them.

So, what does a keto diet specifically do to your gut bacteria? Well, your gut bacteria need fiber to survive. Fiber is their primary food source. And fiber comes almost exclusively from carbohydrates, which includes vegetables and fruits and whole grains and legumes. And as I touched on earlier, if you remove those carbohydrates, then you starve the bacteria that depend on them. Now, that Bath randomized control trial that I talked about earlier found that the ketogenic diet dropped fiber intake to around 15 grams per day, roughly half the NHS recommended intake of 30 grams per day, which still is a bit low, to be honest. And the result was a significant and sustained reduction in something called Bifido bacteria, one of the most important families of beneficial gut bacteria. Bifidobacteria produces B vitamins, it suppresses harmful pathogens, it helps to regulate your immune function, and also helps with the metabolism of cholesterol. The keto group lost those. But the low-sugar group in that study, who still ate whole food carbohydrates, including fiber, had no real change in their gut bacteria at all. And this finding has been replicated across multiple studies. Keto consistently reduces gut microbial diversity, the range of different bacterial species, which is broadly considered to be a marker of a less healthy microbiome. And this is the tension that I flagged up earlier when we were describing what full keto excludes. So, the legumes and the whole grains and the fruits, the foods that you have to give up to maintain full keto, these are the same foods that your microbiome depends on. These two dietary requirements are in direct opposition.

Now, the fourth topic is probably the most interesting one. It's all about adherence. How well do people actually stick to a keto diet over time? This is what we call adherence. And in clinical practice, it is the single most important consideration. And I say that because a treatment that works perfectly in theory, but that people cannot maintain in practice, is in health terms pretty useless. A systematic review published in 2025, analyzing 290 ketogenic diet trials between 2019 and 2024, found that 227 of those trials, so 227 out of 290, 78% lasted less than 6 months. So, that's nearly four in five keto studies do not even run for half a year. And what this means, really, is that we don't have robust long-term human data on proper keto, because quite simply, the people in these trials cannot sustain the diet long enough to generate that data.

Now, the KETO-MED crossover trial, which compared the ketogenic diet directly to the Mediterranean diet over 24 weeks, followed by a 12-week free-choice follow-up, found something really interesting. So, both diets produced metabolic improvements during the structured phase at the beginning. But when people were free to eat as they chose at that 36-week follow-up, dietary patterns had shifted consistently and clearly towards the Mediterranean pattern. So, when people are no longer in this structured trial and can simply eat what they want, they walk away from keto. This is what that trial showed. Is this just a willpower problem? Well, no, it's not. And that distinction matters. It is not, you know, a problem with willpower. It is a structural observation about the diet itself. Proper keto, like full keto, where you restrict carbohydrates massively, is not just calorically restrictive. It is socially, practically, and cognitively demanding in ways that most other dietary changes are not. What this means is that eating out, eating in a restaurant, becomes an obstacle course. Going to a friend's house for dinner requires advanced negotiation. Traveling and shopping and batch cooking and planning snacks and planning your meals and doing the shop and planning how you're going to get energy for a workout becomes really, really complicated. And the diet requires ongoing maintenance of a very specific metabolic state, which means that any slip, you know, a tiny bit of birthday cake, a handful of crisps at a party, can knock you out of ketosis and require days of adjustments to get back into it, if that makes sense.

So, to summarize this really important section, nearly 80% of keto trials last under 6 months, and when followed up freely, people consistently drift away from keto. Adherence, you know, whether somebody sticks to it or not, really is the Achilles' heel of the approach, and it's the most important practical consideration when recommending a dietary strategy for long-term health. There's no point recommending something that we know people don't stick to past 6 months. The best thing to recommend to somebody is a diet strategy that has most of the benefits, but they can easily sustain for the rest of their life.

So, in this section, let's go through the options that you've got to incorporate some form of keto into our diet, because the evidence shows quite clearly that some form of carb restriction is beneficial for you. So, option one, should most people just go full keto? Well, the evidence is pretty clear that full nutritional ketosis works really powerfully in the short term for fat loss and visceral fat reduction and liver fat clearance. But to be honest, for a healthy person who just wants to find a really good approach to their diet and their metabolic health and their longevity, something they can stick to, proper full keto, like proper full keto, where you massively restrict all of your carbohydrates, raises some real concerns across lots of different bodies of evidence, which we've discussed. And that is a consistently replicated rise in LDL cholesterol and apoB, a sustained disruption to your gut microbiome, a cellular aging signal in animal models, and most practically, a failure rate so high that most of the long-term human evidence simply cannot be collected. People cannot stick to keto for long enough. And here's the analogy that I think captures this most clearly. Imagine a medication that worked really well. It reduced your blood sugar. It shifted your visceral fat. It improved your energy. But the dosing schedule was incredibly complex. You had to take, you know, 15 tablets a day at very specific times. And they were all pretty

Big tablets, really difficult to swallow. And the research showed that most people in clinical trials found the regime so difficult that they stopped taking them within 6 months.

Now, as a doctor, would I recommend that medication to most of my patients? Well, probably not. Even if the drug itself was the best drug out there, because I know that most people won't be able to take it. What we would do is look for another medication that perhaps produced slightly smaller benefits, but that came in fewer tablets or smaller tablets and that people could actually take consistently every day for years. Because the medication that gets taken for 10 years will always produce better long-term outcomes than the slightly better medication that gets abandoned after four or 6 months, if that makes sense.

Now, this analogy doesn't work perfectly because what that implies is that full keto is like that big tablet option, the 15 large tablet option. But there's a lot of evidence to suggest that full keto might not be as good as the other option which is simply reducing refined carbs and added sugar.

Anyway, the second option is coming in and out of keto. So, which is better for you long term? Cycling in and out of keto or being in ketosis permanently? Well, the cellular aging data from that mouse study that we mentioned earlier that had planned breaks during ketosis, it suggests that those may mitigate some of the continuous keto concerns that we talked about. And there is some logic to it here. So, giving the body periods of normal metabolic operation interspersed with periods of fat burning could be good for you.

But what would cycling in and out of keto actually look like in practice? Well, there isn't really a standardized evidence-based cycling protocol with long-term human trial data behind it. Various approaches are discussed in the keto community. Some people do 5 days keto, 2 days moderate carbohydrates. Others do four weeks on, one week off. Some do six months of keto and then several months in this Mediterranean style pattern. But none of those have been rigorously tested in long-term human trials with any meaningful outcome data.

And to be honest, the practical reality of coming in and out of keto all the time is a bit more complicated than it sounds. To re-enter ketosis after a break, you typically need several days of very strict carbohydrate restriction under 20 to 50 grams a day while depleting your glycogen stores again. So during that re-entry phase, many people experience what is called keto flu, like fatigue and headaches and brain fog and low mood and poor exercise performance and disrupted sleep as well. This is your body's adjustment to switching fuel systems from burning glucose and glycogen to then burning fat again. And from what I can gather, cuz I've never really experienced keto flu before, it's not pleasant. And it lasts two to five days for most people.

Now imagine doing that every few weeks or every few days if that's how you do it. Every cycle you have a period of feeling a bit unwell and performing worse in the gym or having less energy for your family and your social life and needing to plan your shopping and your cooking and social eating around a very specific set of restrictions. Obviously, not everybody will get keto flu inverted commas, but most people do from what I've read. And then you come off it for a while and you feel normal and then start cycling again. And it just sounds a bit complicated, doesn't it?

And this really matters because health isn't just about your numbers on a blood test. It's about how you feel, how you perform, whether you can be present with the people that you care about, and whether the approach to eating is something that fits into a full and enjoyable life. Cycling keto is a significant cognitive and logistical burden. It is pretty extreme for most people. It requires planning your shopping around two entirely different dietary frameworks. It can impair your exercise performance during a transition week. And for somebody using exercise as part of their overall health strategy, that is a real cost. It disrupts your body's routine, which our biology really does value. The body adapts better to consistency rather than repeated big swings in anything.

And there is also a specific concern with this cycling approach that that Bath randomized control trial highlighted that keto reduces your glucose tolerance, meaning the body becomes temporarily less efficient at handling carbohydrates from a meal. And this appears to be a muscular adaptation to low carbohydrate availability. So when you cycle off keto and you reintroduce carbohydrates, you are doing so with temporarily impaired ability to handle those carbs, which is the opposite of what you want.

Now, could cycling be appropriate for some people? Well, obviously yes. Specifically for people who already have their foundation really solid. If you've absolutely mastered certain parts of your life and you're a really high achiever and you love a challenge, then this could be for you. If you exercise consistently, if you sleep well, if you eat broadly well the rest of the time and you have no underlying cardiovascular risk factors and you want to explore the metabolic effects of periodic ketosis as a tool for optimization, then a structured cycling approach could be a reasonable experiment. I'm not recommending anybody does it, but it could be, you know, sensible for some people. But in my opinion, it's not the best place to start. It's not appropriate advice for somebody who might be overweight or sedentary or confused about nutrition and looking for a good place to begin. And for the vast majority of people seeking long-term health, not rapid short-term fat loss, but actual sustainable longevity habits, I don't think it's the most practical recommendation.

If you need to drop a significant amount of weight quickly or you've got a specific short-term goal, like a medical procedure that requires weight loss or a personal deadline, whatever that might be, then a structured keto or very low calorie ketogenic protocol under medical supervision could be a powerful short-term tool. But that is very different from a dietary strategy for the rest of your life.

And then finally, option three is about cutting just sugars and refined carbohydrates. If you're thinking about doing keto, then this is the approach I would recommend. Rather than doing full keto or cycling in and out of keto just to cut sugars and refined carbohydrates, this is the approach that I think has the most evidence behind it and is the most appropriate for most people over the long run.

So, in terms of that randomized control trial we talked about earlier in the video, simply cutting free sugars and added sugars while keeping whole food carbohydrates including fiber richch foods including root vegetables and legumes, you know, the really good stuff we recommend to eat. Now, in terms of that randomized control trial we talked about earlier, simply cutting sugars and refined carbohydrates, well, keeping these whole carbohydrates in your diet, like legumes and root vegetables, the stuff that we think is really good for you, this actually produced a good amount of fat loss, a 10% reduction in LDL cholesterol, and no change in your APO, which we saw in the other approaches, and also no disruption to your gut microbiome. So you get most of the metabolic benefit, but you avoid the cardiovascular risk problem as well. You preserve your gut microbiome and you keep all the foods that we know are really, really health protective like legumes and whole grains and fruit as well.

Now think about what a diet based on whole foods and fiber and quality protein and healthy fats actually looks like in practice. So breakfast might be eggs with some avocado and a handful of spinach or a bowl of oats with some nuts and berries. Your lunch could be a salad with some chickpeas and olive oil and some fish. Dinner could be a piece of salmon or chicken or a steak with some roasted veg and some lentils. And with this sort of approach, you got lots of variety, lots of color, and lots of goodness in those sorts of food. Nothing is off the table in a way that requires social negotiation or meal bymeal planning like full keto would. You can go to a restaurant with your friends. You can eat at somebody's house without phoning ahead. You can travel. You know, the diet is completely adaptable and adjustable to your life rather than requiring life to adapt to the diet.

And here's something else that's worth mentioning at this point. If you remove ultrarocessed foods from your diet, which provides roughly 2/3 of the added sugar and refined carbohydrates in the average western diet and you replace it with whole foods, you automatically cut your sugar intake. You automatically increase your fiber intake. You automatically diversify your gut microbiome and automatically reduce your overall glycemic load. So, you don't need to track your carbohydrates or track your macronutrients or where your food. You just stop eating the biscuits and the fizzy drinks and the white bread and the processed snacks and the ready meals. And when you do that, you automatically have a diet that is incredibly good for you and automatically gets rid of the refined carbohydrates and added sugar that gives you most of the benefit of keto.

So, which dietary pattern has the strongest long-term evidence for keeping people alive and well? Well, when we talk about what keeps people healthy, not over 12 weeks in a clinical trial, but over decades of real life, there is one dietary pattern that has more human evidence behind it than anything else. You've probably heard of it called the Mediterranean diet. And I want to be clear about what that term actually means and what it doesn't mean. The Mediterranean diet is not a rigid meal plan. It does not mean eating specifically Italian or Greek food. The reason it's called the Mediterranean diet is simply that the traditional eating patterns of populations around the Mediterranean happens to be one that researchers followed for the longest time and in the largest populations. You do not need to live anywhere near the Mediterranean to eat this way. The name is essentially a historical accident.

What it actually describes is this. A diet built primarily around whole, minimally processed foods, plenty of veg, as many different colors and types as you can get because different veg feed different gut bacteria and provide different nutrients. It means legumes, so things like lentils and chickpeas, which we eat pretty much every day. beans eaten regularly because they are absolutely massively rich in fiber and protein and compound and reduce your cardiovascular risk over time. This is what the evidence says. It also means whole grains, so things like oats and brown rice and barley and quinoa and whole grain bread specifically like fermented seeded sourdough which provide the fiber that feeds your gut and slows down digestion. It also means good quality protein like fish, particularly oily fish and eggs and poultry and a small amount of red meat as well and modest amounts of dairy and also healthy fats like olive oil and nuts and seeds and avocado and very little in the way of ultrarocessed foods and added sugar or refined carbohydrates. Anything basically that comes in a packet with more than five ingredients on the label.

Now clearly apart from trying to reduce ultrarocessed foods that is not a restrictive diet. That is a massive you know array of things that you could be eating every single day. It is not restrictive in its nature. You can call it what you like. A whole food diet or an anti-inflammatory diet or a longevity diet or call it the Mediterranean diet if you want. The label doesn't really matter. What matters is the pattern. And that pattern has extraordinary long-term evidence behind it.

Now, as an example of that, a metaanalysis of 29 observational studies covering over 1.6 million people found greater adherence to this kind of diet was associated with a 10% reduction in all cause mortality, dying from any cause. Another study, a 25 year cohort study of over 25,000 women, one of the longest dietary follow-up studies ever conducted, found that those eating closest to this pattern, had a 23% lower risk of dying during that study time with improvements in inflammatory markers and insulin resistance, um, blood pressure and weight as well. And then another study for you, a systematic review covering over 158,000 older adults found that high adherence to this sort of dietary pattern reduced all cause mortality by 23% and cardiovascular mortality by 27%.

Now the important thing to mention is that these are observational studies. They watch what people eat and then what happens over time. They cannot definitely prove that the diet itself caused the better outcomes because people who eat this way also tend to exercise more and smoke less and sleep better and generally make a broader range of healthy choices. The diets may partly be a marker of a healthconscious lifestyle rather than the sole driver of the benefit. But does that make the evidence less useful? Well, I would argue the opposite. If eating whole foods and prioritizing fiber and protein and healthy fats and cutting out ultrarocessed food tends to go handinhand with better sleep and more exercise and other positive lifestyle choices, that absolutely is not a reason to dismiss it. That is the point of this. These things feed into each other. When you start eating better, you have more energy to exercise. You then sleep better. you then make better food choices the next day because you feel more refreshed and you're craving less sugary food. And then when you're not relying on ultrarocessed food, you are cooking more. You're engaging more with what you eat. And you're building habits that compound over time. We're talking about the rest of your life here, preventing or delaying the moment that you die. So that could be 10, 20, 40, 50 years or whatever. So whether you call it the Mediterranean diet or a whole food diet or simply eating like a sensible person like our ancestors would have done, the evidence consistently points to the same cluster of behaviors and they reinforce each other. Just remember, we're talking about 25 years, hundreds of thousands of people, a 23% reduction in your risk of dying. That is the kind of long-term human evidence that full keto simply doesn't have and cannot have because most people cannot maintain it long enough to generate that sort of data. And if you're going to pick an eating pattern that prolongs your life, then it has to be a pattern that you can sustain over decades.

So after all of that, what should you actually do regarding keto? Should you do keto? Should you not do keto? Should you sort of cycle in and out? Do you just cut carbs and keep everything else? Well, here's what I think. The underlying insight here that metabolic dysfunction and insulin resistance drive so much of the chronic disease that kills people and that getting the body to burn fat rather than being permanently flooded with glucose and insulin is a really worthy goal. It's something that we should aim for and that is absolutely correct according to the evidence. But where I think keto as a dietary prescription goes wrong is in the practical implementation for most people, not everybody, but for most people. You know, the average person watching these videos. My absolute sort of gut feeling is that the body doesn't like extremes. And for me, that's not a philosophical position. It is built into our physiology. Every system in the body operates within a regulated range. is called homeostasis. When you push hard in one direction, the body adapts, but adaptation has costs like LDL going up like we talked about, your gut bacteria being disrupted, the cellular aging signal in the animal study that we talked about. These are the costs of a state the body was not designed to sustain indefinitely. Ketosis, remember, is a survival mechanism. It is not a baseline setting.

So, what do I actually recommend? Well, for someone who wants to drop significant weights quickly, and I wouldn't recommend that, but just say you do, who has a specific medical or personal reason to achieve rapid fat loss, like you know, you need to lose weight for a surgery, then a structured ketogenic protocol or very low calorie ketogenic diet under medical supervision could be a good short-term tool. not for everybody but for some people. The evidence seems to support it for that purpose over the short term. But that is not the same as a lifetime dietary strategy. These people who want to live well and live long, we need to pick something that will work for 30 or 50 years.

For the majority of people watching this who feel overwhelmed by conflicting dietary advice, who want to genuinely improve their long-term health, who want to reduce their risk of cardiovascular disease and cancer and dementia, and who want a way of eating that they can maintain for the long run, here's what you should do. So, you should be eating mostly whole foods. You need to be cooking and preparing your own meals as much as you can. You need to have a proper breakfast. So that isn't cereal or toast with jam or a cross or anything sweet because anything sweet for your breakfast is a dessert. It means things like an omelette or scrambled eggs or dippy eggs or smoked salmon or Greek yogurt with some nuts and berries and seeds. It means something that will actually fill you up, that is actually whole food and that doesn't spike your insulin before 8:00 a.m. It means eating three proper meals a day. eating enough protein and fiber at each of those meals to feel genuinely satisfied at the end of it. So that snacking between meals becomes unnecessary. You should arrive at your next meal feeling a bit hungry but not ravenous for snacks but you know genuinely ready to eat your next meal. You know because that hunger between meals is really important. It means that your insulin levels have returned to baseline. you're not constantly snacking all the way through the day, keeping your blood sugar elevated and your insulin elevated as well.

Remember the fuel priority order that we talked about earlier. So glucose comes down relatively quickly after a meal, but insulin always stays elevated for a bit longer. So if you're snacking continuously, you are keeping your insulin level elevated all day, which means you are never giving your body the chance to shift into fat burning mode. And it also means protecting your overnight fast. This is one of the most powerful metabolic interventions available to you and it costs absolutely nothing. It means that you know eating your last meal at around 6:00 or 7 in the evening and then having your breakfast at 7 or 8 in the morning. So that is a 13 to 14 hour overnight fast. And I would say that's the bare minimum that you should be aiming for. During those hours, your body works through the fuel priority order that we described earlier, depleting its immediate glucose supply, then working through its glycogen stores and then by the early hours of the morning, quietly burning fat and producing low levels of ketones. And like I said earlier, this isn't, you know, a strict sort of cut off where you switch from one to the other. All of it overlaps, but the longer that you can stretch your overnight fast for, the more ketones you're going to be generating by the morning. So basically, you're going very quietly and very gently ketogenic every single night without any restriction, without the keto flu, without any of the downsides of the full ketogenic diet, and without excluding any foods apart from the stuff that's bad for us anyway, like ultrarocessed food and refined carbohydrates.

Now over weeks and months that regular overnight metabolic reset accumulates. Your body gets regular practice at burning fat. Your liver fat and your visceral fat will gradually reduce. Your insulin sensitivity will improve. Now the key behaviors that protect this fasting window are pretty simple. It means not eating late at night. Do not snack after dinner. If you're genuinely hungry in the evening, then eat a bit more at dinner. Eat more of the good stuff because this food is sort of like medicine for you. Protect those overnight hours of fat burning as much as you can. Then through your eating day, think about how to occasionally push a little deeper into that fat burning state, not by going full keto, but by the natural consequence of whole food eating. And also, if you exercise in the morning before your breakfast or you go for a long walk, you'll burn through more of that glycogen and push closer into the sort of mild ketosis state. If you have a busy day and eat later than usual, then the fasting window will extend naturally as well. None of this requires a rigid protocol like the proper keto diet does. It happens as the byproduct of eating well and protecting your fasting window and moving more.

And perhaps the most important point about all of this is to try and reduce or cut out ultrarocessed foods as much as you can because ultrarocessed food is more than anything else the primary driver of excess added sugar of excess refined carbohydrates and excess calorie density in the modern western diet. So if you remove it then the rest of your diet will improve. Your fiber intake will naturally go up. Your gut microbiome will improve. Your blood glucose becomes more stable. Your insulin levels spend more time at baseline. You naturally eat less, not because you're counting calories, but because whole foods are more satisfying per calorie. They keep you full for longer. So what you end up with if you follow this approach is a diet where your carbohydrate intake consists almost entirely of really really good foods, fiber richch whole food sources. And according to the evidence, that is the best approach for the average person watching this video. You get most of the benefits of keto and also the good chance that you're going to sustain that over your lifetime. And really the best pieces of medical advice that we can give you are things that you can sustain over the long run.

So I really hope you found that video useful today. That has been a long one. Please let me know if you found this length useful, this level of detail useful, or whether just a 10-minute video sort of skimming the surface would be better for you. I really really appreciate all your feedback and I will see you in the next.