Why we can't eat just one

We do it for the buzz. Like drug addicts. How do we stop the constant craving?

Published June 18, 2009 10:20AM (EDT)

Dr. David Kessler, 58, says that when he looks at a huge plate of French fries, he knows that if he starts eating them, he won't stop until he's wolfed them all down. Yes, even the former head of the Food and Drug Administration, who once oversaw the nation's health, struggles to eat well like the rest of us.

In his new best-selling book, "The End of Overeating: Taking Control of the Insatiable American Appetite," Kessler, a San Francisco Bay Area pediatrician, explains why certain foods loaded with fat, sugar and salt exert such a pull, despite our best intentions to avoid them. As he discusses the biology that leads to scarfing down a plate of fries, he delves into such puzzles as why the French fry binger is more likely to remember the pleasant stimulation of the fries' salt, fat, texture and flavor than the stomachache and self-recrimination that follow it.

The former dean of medical schools at Yale and the University of California, San Francisco, Kessler, who is also a lawyer, contends that the American food culture, including our mores about when, where and how often we eat, plays a large role in fostering what he calls "conditioned hypereating." He argues that the government, food industry and individual diner all have parts to play in combating that plate of fries. While Kessler is not offering a weight-loss solution or proposing some chimerical healthy eating plan, his book strips away the allure of some of the most appetizing and unhealthy foods. I spoke with Dr. Kessler about why so many of us can't eat just one.

What do you think is the biggest misconceptions about why people overeat?

That it's a matter of willpower, that you can just use self-control. I think a lot of people don't understand why it's so hard to resist food.

What is going on in the brain when you start thinking about a very desirable food, like a potato chip or a chocolate-chip cookie?

The power of food comes not only from its taste but from that anticipation. That anticipation is based on prior experience, learning and memory. Something's going to set off that anticipation, those thoughts of wanting.

When I'm flying into San Francisco airport, as soon as the plane hits the ground, I start thinking about Chinese dumplings at the airport food court because I've been there before. It creates that arousal, that slight anxiety. And what does that do? It grabs our attention. It occupies our working memory. Our brains get activated. We can now look at the imaging of which circuits and areas of the brain get activated, and we see in millions of people that anticipation results in excess activation of the amygdala, part of the brain's reward circuits.

What happens once you start eating?

In people who have a hard time controlling their eating, their brain circuits remain elevated and activated until all the food is gone. Then the next time you get cued, you do it again. Every time you engage in this cycle you strengthen the neural circuits. The anticipation gets strengthened. It's in part because of ambivalence. Do you ever have an internal dialogue? "Boy, that would taste great. No, I shouldn't have it. I really want that. And I shouldn't do it."

That sort of ambivalence increases the reward value of the food. It increases the anxiety, it increases the arousal, it keeps it in working memory. We're wired to focus on the most salient stimuli in our environment. For some people it could be alcohol or illegal drugs or nicotine or sex or gambling. For many of us it's food.

Are you saying if you give in to the craving and eat whatever the desirable food is, it's more likely that you're going to do it again?

It's basic learning. When you get cued, the brain gets activated. There's an arousal. There's increased dopamine. That dopamine focuses your attention. It narrows your focus. Of all the stimuli in the environment, why does that chocolate-chip cookie have such power?

We're wired to focus on the most salient stimuli. What do I mean? If a bear walked in right now, you're going to stop focusing on this interview. It's part of being human. It's what's made us successful as a species. You make food hyper-palatable with fat, sugar and salt. It's very stimulating and it becomes the most salient stimuli for many people.

What makes a food hyper-palatable? Even if you like apples, you're probably likely to eat one and not gorge yourself on four more. Where if you like nachos, you might eat way more than you had intended to when you started. What is the difference between these foods?

It starts with how many chews there are in a bite. If you take a stimulus and you get a sensory hit and it disappears, what do you do immediately next?

You take another bite.

Yes. We're eating, in essence, adult baby food. Twenty years ago the average chews per bite was about 20, now it's two or three. The food goes down in a whoosh and it's very stimulating. It's layered and loaded with fat, sugar and salt. It's as if you have a roller coaster going on in your mouth. You get stimulated, it disappears instantly and you reach for more.

Of fat, sugar and salt, which is the most potent in this way?

I published a paper called "Deconstructing the Vanilla Milkshake" with my colleagues at Washington State University. We asked: Is it the sugar, is it the fat, is it the flavor? Sugar is the main driver, but when you add fat to, it's synergistic. So it's more potent.

But it's not any one substance. Nicotine itself is only a moderate reinforcer. But add the smoke, throat scratch, crinkling of the cellophane pack, color of the pack, imagery that was created 40 years ago that it was cool to smoke, emotional gloss of advertising, and what did we end up with? We ended up with a deadly addictive product.

So I give you a package of sugar and say, "Go have a good time," you're going to look at me and say, "What are you talking about?" But I add fat, I add texture, I add temperature, I add color and I add flavor. I put it on every corner and say, "It's socially acceptable to eat any time." I say, "You can do it with your friends. You can do it at the end of this day. You can relieve any tension." We're eating in a disorganized and chaotic fashion. And we're being bombarded with the cues.

We make food into entertainment. We make it into a food carnival. Go into a modern American restaurant: the colors, the TVs, the monitors, the music. You do it with your friends. We've taken sugar and added all these multiple levels of stimuli. What do we end up with? Probably one of the great public health crises of our day.

Doesn't fat make food easier to swallow without much chewing?

Absolutely. It also enhances the sensory aspect in multiple ways. I used to think that I was eating for nutrition. I was eating to satisfy myself, to sustain myself. We're eating for stimulation.

How has the scientific understanding of overeating changed in the last few decades?

Many people still think the reason that they keep on gaining weight is their metabolism. There may be some contribution of metabolism to body weight but it's relatively small. What's really driving consumption is what's going on in your brain.

Going back through the 1960s, weight was relatively stable. It was flat over an adult lifetime. You gain a few pounds from ages 20 to 40. You level off. You'd lose a few pounds in your 60s and 70s. But weight was relatively flat throughout your adult years.

Now, decades later, weight continues to increase, even in the adult years. But what's most striking is that you enter your adult years -- just look at the weight of 20-year-olds -- when you begin your adulthood, you're much, much bigger on average.

We used to think our bodies would regulate our weight, that there was a set point. That's why if we went on a diet we would gain it back, because we had a predetermined weight. But if that were the case we wouldn't all be getting bigger and bigger.

There may be what's called a settling point. But a lot of that settling point is driven by how your brain reacts to these cues and how sensitive you are to responding to your environment. The availability of food affects your settling point. There's no predetermined genetic set point.

Why are diets so prone to failure?

The reason diets don't work in the long run is if you have that old circuitry, that old learning, and you respond to those cues. Sure, I can take you out of your environment. I can give you meal replacements, or you can white-knuckle it, and for 30 days, 60 days, 90 days, resist eating a lot of food, and you can lose weight, no question about that.

Now your diet's over. I put you back into your environment. You still have that old learning, that old circuitry. What's going to happen? You're going to get bombarded with the cues again and you're going to gain it back if you have not laid down new circuitry and new learning on top of that old circuitry.

What do people who struggle with overeating have in common?

Loss of control in the face of palatable foods and a hard time resisting foods; a lack of feeling full and a hard time stopping eating; a preoccupation or thinking about foods between meals. Even when you're eating certain foods, you're thinking about what you're going to eat next.

Do those people who experience what you call conditioned hyper-eating experience more pleasure than other people?

No! That's interesting. It's not that there's greater pleasure. It's just that they have greater sensitivity to the cues, greater thoughts of wanting, and that stimulates and activates their brain.

So their anticipation is greater?

Yes. Absolutely. And it's much harder for them to resist. They don't taste food any differently than anyone else but they have a much greater struggle with the anticipation of food.

When you talk about this being conditioned, do we know if some people were born with this capacity, or if it was just created over time by their environment, or are we not really sure?

We don't know which one weighs more heavily, genetics or the environment. But if you look at 2-year-olds, they compensate for their eating. If you give them more calories at lunch, they'll eat fewer calories for the remainder of the day. By the time these kids are 4 and 5, they lose the ability to compensate. Given the exposure to fat, sugar and salt when they're 3, 4 and 5, the reward pathways of the brain take over and hijack the normal body's homeostatic mechanism to regulate itself. It used to be that 3-, 4- and 5-year-olds compensated, and fewer of them compensate today. That kind of change suggests environmental forces, that learning has a profound consequence.

When you think about it, we're conditioning the brains of millions of our kids and that conditioning, that neural circuitry laid down after exposure to highly palatable foods, lasts a lifetime. It has profound consequences not only for the individual but also for public policy.

Why do you think there's so much guilt, shame and blame when it comes to talking about overeating? Because people don't understand their own behavior?

I didn't understand my own behavior and I was commissioner of the Food and Drug Administration. I regulated food. I was trained as a physician. I didn't realize: Why does that chocolate-chip cookie have such power over me? Is it something about that chocolate-chip cookie? Or is it how my brain encodes that representation of that chocolate-chip cookie?

What do you think the government should be doing to regulate the food industry to create a better food environment?

The government has two major roles: greater education and certainly greater disclosure. When you recognize that the food that's being sold is hijacking the brains not just of adults but of kids, that has implications for school lunches, for vending machines in schools and farm subsidies.

What part of that is up to the individual?

I think individuals have to protect themselves. You have to understand your brain's being activated. You have to understand when you walk down the street that you're being bombarded. You have to understand that these are false signals. It's going to seem like you're hungry all the time.

The thoughts of wanting to eat overwhelm you, whether or not you're hungry?

Absolutely. Those thoughts of wanting are very real to me. My brain's being activated, the raw pathways to the brain are sending : You know you want that food!

This might have been a good adaptive strategy in the past. But now it's backfiring, right?

Those who can focus on the most salient stimuli for food when there was a scarcity of food would remember the location, they would remember the cues, they would be able to get the food to survive. Just think about it: Take a bird, an insect. How are they going to find the food? The location, the cues, being able to have their brain wired so that those cues trigger where the food is. That's very much an adaptive strategy for survival.

Do people of all sizes and weights have this tendency to overeat?

Absolutely. Our data suggests that a greater percentage of obese individuals and overweight individuals have this. But a significant percentage of lean people have it. If you say to them -- "Do you have a hard time resisting? Do you think about foods? Do you have a hard time stopping?" -- a significant percentage of lean people say, "That's me."

The question is, how have they stayed lean? For many of them the fact is, they're in torment. It's a constant struggle. Others have laid down new learning, and that's made it easier. They develop rules for themselves that they follow. Then, you're not constantly eating in a chaotic, disorganized way. You're not constantly being cued. Your brain's not being constantly activated. But those rules have to be unambiguous, and they're not easy to follow.

In the end, they have what's called a critical perceptual shift. They look at food differently. How do you really cool a stimulus? How do you decrease the anticipation of the food, the power of the food to activate, to grab attention? The answer to that is you view the stimulus differently.

If you look at a huge plate of fries and say "That's my friend, that's going to make me feel better, I want that," that's only going to increase the level of anticipation. You look at that huge plate of fries and say, "That's not my friend, that's going to make me feel pretty crummy in 20 minutes. I don't want that," and you internalize that, then you can decrease the anticipation.

But if you have any doubts, if you have this back-and-forth debate in your head -- "Boy that's great. I shouldn't have that" -- that only increases the anticipation more.

What's the great success with tobacco? Did we change the product? No. We changed how the product was perceived. It used to be perceived as something that was glamorous, something that people wanted to do that was cool. We changed the perception, the social norm. It's now viewed as a deadly, disgusting, addictive product. Where it was once positively valenced, as scientists call it, we made it negatively valenced.

But isn't the problem with that comparison is that it's the quantity of food that makes it bad for your health. If you could just eat a few bites of nachos, it wouldn't be that bad. So how can you look at a plate of nachos like it's a cigarette?

You're exactly right. You can't demonize food. We need food. So how do you control it? Tobacco was easy compared to food. Some people -- and I'm not advocating it -- become vegetarian. That makes it easier. They look at animal fats and proteins and say, "I don't want that." Some people look at food and say, "That's highly processed, I don't want that. I want real food." Some people look at large portions and say, "I don't want that, that looks disgusting."

I'm not a food purist. Don't get me wrong. If you want to go into Kentucky Fried Chicken and have three chicken strips, that's fine. If you want to eat a hamburger and it's 500 calories, that's fine. It's when you take that 500 calories and make it into 1,000, 1,500 or 2,000. That's where the real damage is done.

But how is laying down new learning or creating rules any different than the call to have willpower?

Rules can help calm down the brain activation. If you say to a smoker, "You can't smoke for the next four hours. It's impossible," that's calming. On a plane, no smoker opens the emergency exit mid-flight and says, "I need a cigarette." It's because they know it's impossible. It cools down the stimuli.

I got to the point where I said, "I'm not going to eat French fries because I know if I eat them, I'm going to finish all of them." There's just no way I'm going to be able to resist. And now when I look at French fries I don't have thoughts of anticipation. My brain doesn't get activated, because I've been able to internalize that rule and I follow that rule and it becomes automatic.

Is that the best way to make super-tempting food lose its power over you?

It's a very important question. Now that we know the brain is becoming activated and hijacked, the question is, What's the best way to cool off the stimulus? Do you want to take away the cue entirely and not expose the person? Or do you want to expose the person and say you can't eat it, and decondition that way? We don't have the science yet on what's the best way, the most effective way, to cool the stimulus.

It also depends on what kind of state you're in. Once that old circuitry is laid down, if you stress me, if I'm fatigued, if I feel deprived, and you put that chocolate-chip cookie in front of me, I'm going to eat it.

Other times, if my super cortical control, my frontal lobes are working, I'm not stressed, I'm not fatigued, I'm not deprived, that old circuitry is not going to show its head. It's part of being human. We haven't explained that to people. There are times when we're going to fall off the wagon and we'd be less than human if we did not.

And that's OK?

It's the way it's going to be. It's not perfect. Once you have that old circuitry, that old learning there, it's going to show its head sometimes. And we just have to recognize and accept that there's nothing wrong with it. It's just the way our brains are designed. When we're stressed, when we're cued, the reward value of food increases. In some instances, we're eating just to calm ourselves down. It's very real.

What people need to do is to recognize what's driving their behavior. It's not that they can be perfect and never engage in that behavior, but if they know what's driving that behavior, then they can at least take steps to plan for it and make it less harmful.

Isn't the food industry's entire business model built on catering to, and encouraging the kind of hyper-eating you're describing? Can we really expect them to change any of their practices?

It does go against their business model. But where I think that it crosses the line, where we can expect and should expect them to show some corporate citizenry, is to control portion size. The fact is, once your brain gets stimulated, you're going to eat everything in that package. As they make the package bigger, we're going to consume more. Knowing that, at least they can put some brakes on.

The other thing is greater disclosure. Just taking fat, sugar and salt and putting it in a lot of different forms, a lot of different colors, and selling it constantly, doesn't contribute to the nutrition of the nation. Maybe that's asking for more than we can expect. You know the joke in the industry: "When in doubt, just add bacon and cheese to it."

By Katharine Mieszkowski

Katharine Mieszkowski is a senior writer for Salon.

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