Transcription
[Music] Can you imagine a blessure so intense that you would be willing to give up everything you care for: your family, your friends, your health, your freedom, just to temporarily experience it? I certainly could not. Yet this was the way that the behavior of addicts was explained to me when I was a medical student, and the way it's still explained by many in the healthcare system—a perspective that has helped promote the notion of addiction as moral failure. But it's more incomprehensible than that, because my addicted patients could not understand it either. They said that the drug was no longer even pleasurable, and yet they could not stop taking it. And this loss of control over one's own behavior intrigued me so much that I've been trying to understand how this would happen. But where do you start?
By then, we already knew from animal experiments that all of the drugs that produce addiction increase dopamine in the brain reward regions, activating them. However, what happens in that transition from being able to occasionally enjoy a drug into the compulsive administration of addiction was a complete mystery. I was very lucky that, as I was finishing medical school, a new technology had emerged: positron emission tomography, that enabled us, for the first time, to image the living human brain. To me, as a young scientist, this was like science fiction, because it provided me with a tool that I could use to compare the function and biochemistry of the brain of a person that was addicted to drugs from that of someone who was not. And this image here illustrates our first findings, initially reported in cocaine abusers, that we went on to replicate in methamphetamine abusers, alcoholics, heroin abusers. And what we found was that the brain of addicted individuals had a reduction in the levels of dopamine D2 receptors. Dopamine D2 receptors regulate the function of the frontal areas of our brain that allow us to exert self-control, thus providing an explanation about why an addicted person would be more vulnerable to impulsive and compulsive drug administration.
These findings made me start to wonder whether something similar could be happening in obesity, because, after all, most of these individuals want to lose weight, but they cannot control their food intake. So the same question: Can you imagine food being so pleasurable that you are willing to forgo 10 years of your life because of the adverse health consequences from obesity, or undergo the stigma from the disapprovals cast by others because you cannot hide obesity? I certainly cannot think of such a food. Those we have applied the same methodology to investigate morbidly obese individuals, and what we found was that, just as for addiction, their brains had a reduction in the levels of dopamine D2 receptors, indicating to us that this was a biochemical signature of a brain where the capacity to control strong urges has been compromised.
But why? Why? Why would this happen? Our brains are hardwired to respond to rewards, which then motivates our actions. Reward is a brilliant solution to ensure that we will do behaviors that are indispensable for the survival of the individual and of the species, because, after all, if food or sex were not rewarding, we would not eat or procreate. And dopamine is the chemical that signals reward in our brains. Interestingly, dopamine is increased not just by rewarding pleasurable stimuli, but also by stimuli that predict a reward, which we call conditioned stimuli. And again, this is a brilliant solution, because when you increase dopamine in your brain that enhances the motivation and sustains the drive for you to do the behaviors that are necessary to procure the reward, therefore ensuring that you will go and get the food so you can eat it, for example. This great-looking chocolate—that visual of this great-looking chocolate is making me want to eat it now, and if I had it now, I would eat it. My brain is conditioned to chocolate, so that mere visual is making my brain predict that it's going to get a reward, and dopamine is going up in my brain just by visually observing that stimuli, which then makes me want to eat it. Most of the time I am actually able to resist that urge of wanting to eat that chocolate; sometimes I fail, and I feel very guilty later, and I find myself that I'm much more vulnerable to failing and to not be able to resist the temptation when I'm hungry, and the hungrier I am, the worse it gets. But this makes sense: when my brain is hungry, and particularly if I am starving, my brain gets into a state that I like to call “of deprivation.” In the state of deprivation, the main priority of my brain is to find the food so I can eat it, because for most of human evolution food was scarce and hard to come by, so you want to ensure that you would pay attention so that you would do the behaviors so that you could eat, because otherwise you may not survive. However, in our current environments where food is everywhere, this has become a liability, and in fact I find myself constantly actively having to suppress the urge to eat all of this extraordinary-looking food that is everywhere. Food stimuli are everywhere: visuals, auditory, smell. And when I eat the food, when I cannot resist it, I eventually feel satiated, and when I'm satiated the food stops being rewarding to my brain, which then, of course, enables me to change my behaviors and to do things that in the past may have had an advantage over my survival later. However, our modern societies have engineered highly rewarding food that can bypass that satiety mechanisms. These are foods that are rich in sugar, fat, and salt, and these are foods that can trigger compulsive overeating in almost everyone. These foods are the ones that can create havoc in the brain dopamine reward system. Highly rewarding food, just like drugs, produce sharp and short-lasting increases in dopamine, and the repeated and frequent administration progressively leads to a loss of dopamine D2 receptors, which then compromises our ability to control the strong urges to eat this very appealing food.
Obesity, just like addiction, represents extreme consequences of the disruption of the systems in our brain that enable us to balance between immediate rewards that enable us to take care of immediate needs and behaviors that may have an advantage later, once those immediate needs have been accomplished. Addiction and obesity have been stigmatized and dismissed as disorders of poor self-control—self-inflicted personal behavioral choices. You know, I've never ever met an addicted person who wanted to be an addict, nor have I ever met an obese person who wanted to be obese. Their dismissal as just problems of self-control—can you imagine? Can you imagine what it must be like to want to stop doing something and not be able to do it? And you try, and you fail, and you try again, and you fail again and again, and you start hating yourself for not being able to do it? I don't need to imagine. I can remember my grandfather took his own life at his inability to control his alcoholism—one final and last relapse and his surrender to self-hatred. Or my obese adolescent patient who contemplated suicide to escape the relentless and cruel bullying from her peers. Dismissal of addiction and obesity as just problems of self-control ignores the fact that, for all to be able to exert self-control, we require the proper function of the areas in our brains that regulate our behaviors. In simple terms, and taken to the extreme, it's like driving a car without brakes: no matter how much you want to stop, you will not be able to do it. Some of us, because of our genetics, our developmental trajectories, our social circumstances, are more vulnerable to these disorders than others. And though we don't know yet how to remediate the genetic and developmental vulnerability factors, we already have the tools to address the problem of obesity and of addiction, because, for the most part, obesity and addiction can be prevented. The current problems that we are facing of obesity are not the result of mutations in our genes but of the dramatic changes in our environment that have occurred over the past decades. We humans excel at our ability to change environments, so why can we not re-engineer them so that instead of making us vulnerable they strengthen our biology? We know how to prevent obesity; we've done it in the past in small communities. The challenge is not not knowing how to do it; the challenge is in committing the resources now to create an infrastructure that provides with options and alternatives—but real options and real alternatives. Why can't we not have food that is healthy, appealing, accessible, and affordable? Why can we not generate environments where that promote rather than hinder physical activities? The challenge is in committing the resources now to build an infrastructure that will provide with real alternative and real choices for everyone, not just those that can afford it. Some will argue that creating such an infrastructure will be costly now. One can counter-argue that this will be more than offset by all of the savings from averted medical costs, plus the economical growth of a new food industry. So can we? Can we all imagine committing now—committing now for something that will provide us a much greater social benefit later? I certainly can. It makes sense. Not only will we save lots of money from averted medical consequences, but we will improve the health of all of us and that of future generations.
Thanks. [Music]