Why We Get Fat: And What to Do About It (20 page)

This is not a coincidence. It’s clear from animal research that the foods animals will preferentially eat perhaps to excess are those that most quickly supply energy to the cells—easily digestible carbohydrates.

But another factor is how hungry we are, which is another way
of saying how long it’s been since our last meal and how much energy we’ve expended in the interim. The longer we go between meals and the more energy we’ve expended, the hungrier we’ll be. And the hungrier we are, the better foods will taste:
Wow! That was great. I was starving
. “It is often said and not without reason,” as Pavlov wrote more than a century ago, “that ‘hunger is the best sauce.’ ”

Even before we begin eating, insulin works to increase our feeling of hunger. Remember, we begin secreting insulin just by thinking about eating (and particularly eating carbohydrate-rich foods and sweets), and this insulin secretion then increases within seconds of taking our first bite. It happens even before we begin to digest the meal, and before any glucose appears in the bloodstream. This insulin serves to prepare our bodies for the upcoming flood of glucose by storing away other nutrients in the circulation—particularly fatty acids. So our experience of hunger actually increases just by thinking about eating, and then it increases further with the first few bites we take. (The French have a saying for this: “
L’appétit vient en mangeant,
” the appetite comes while eating.)

As the meal continues, this “metabolic background of hunger,” as the French scientist Jacques Le Magnen called it, begins to ebb, our appetite is satisfied, and our perception of the palatability of the meal, how good it tastes, diminishes as well. The insulin is now working in the brain to suppress appetite and eating behavior. As a result, our first bites of a meal will invariably taste better to us than our last bites. (This is why the phrase “good to the last bite” is used to describe a product or experience that is particularly tasty or enjoyable.) This is the likely physiological explanation for why so many of us—fat or lean—become so fond of pasta and bagels and other carbohydrate-rich foods. Just by thinking about eating them, we secrete insulin. The insulin makes us hungry by temporarily diverting nutrients out of the circulation and into storage, and this, in turn, makes us savor our first bites even more than we otherwise would. The greater the blood sugar and
insulin response to a particular food, the more we like it—the better we think it tastes.

This palatability-by-blood-sugar-and-insulin response is almost assuredly exaggerated in people who are fat or predisposed to get that way. And the fatter they get, the more they’ll crave carbohydrate-rich foods, because their insulin will be more effective at stashing fat and protein in their muscle and fat tissue, where they can’t be used for fuel.

Once we get resistant to insulin, which will happen eventually, we’ll have more insulin coursing through our veins during much, if not all, of the day. Hence, we’ll also have longer periods during every twenty-four hours when the only fuel we can burn is the glucose from carbohydrates. The insulin, remember, is working to keep protein and fat and even glycogen (the storage form of carbohydrates) safely stashed away for later. It’s telling our cells that there is blood sugar in excess to be burned, but there’s
not
. So it’s glucose we crave. Even if you eat fat and protein—a hamburger without the bun, say, or a hunk of cheese—the insulin will work to store these nutrients rather than allow your body to burn them for fuel. You will have little desire to eat it, at least not without some carbohydrate-rich bread as well, because your body, at the moment, has little interest in burning it for fuel.

Sweets, again, are a special case, which probably won’t be a surprise to anyone with a sweet tooth (or anyone who’s ever raised a child). First, the unique metabolic effects of fructose in the liver, combined with the insulin-stimulating effect of glucose, might be enough to induce cravings in those predisposed to fatten. But then there’s the effect in the brain: when you eat sugar, according to research by Bartley Hoebel of Princeton University, it triggers a response in the same part of the brain—known as the “reward center”—that is targeted by cocaine, alcohol, nicotine, and other addictive substances. All food does this to some extent, because that’s what the reward system apparently evolved to do: reinforce behaviors (eating and sex) that benefit the species. But sugar seems to hijack the signal to an unnatural degree, just as
cocaine and nicotine do. If we believe the animal research, then sugar and high-fructose corn syrup are addictive in the same way that drugs are and for much the same biochemical reasons.
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Now, how’s that for a vicious cycle? The foods that make us fat also make us crave precisely the foods that make us fat. (This, again, is little different from smoking: the cigarettes that give us lung cancer also make us crave the cigarettes that give us lung cancer.) The more fattening they are, and the more predisposed you are to get fat when you eat them, the greater the cravings. The cycle can be broken, although it requires fighting these cravings—just as alcoholics can quit drinking and smokers can quit smoking, but not without constant effort and vigilance.

The simple answer to the question of why we get fat is that carbohydrates make us so; protein and fat do not. But if this is the case, why do we all know people who have gone on low-fat diets and lost weight? Low-fat diets, after all, are relatively high in carbohydrates, so shouldn’t these fail for all the people who try them?

Most of us know people who say they lost significant weight after joining Weight Watchers or Jenny Craig, after reading
Skinny Bitch
or
French Women Don’t Get Fat
, or following the very low-fat diet prescribed by Dean Ornish in
Eat More, Weigh Less
. When researchers test the effectiveness of diets in clinical trials, like the Stanford University A TO Z Trial that I’ll discuss shortly, they’ll invariably find that a few subjects do indeed lose considerable weight following low-fat diets. Doesn’t this mean that some of us get fat because we eat carbohydrates and get lean again when we don’t, but for others, avoiding fat is the answer?

The simple answer is probably not. The more likely explanation is that any diet that succeeds does so because the dieter restricts fattening carbohydrates, whether by explicit instruction or not. To put it simply, those who lose fat on a diet do so because of what they are not eating—the fattening carbohydrates—not because of what they are eating.

Whenever we go on any serious weight-loss regimen, whether a diet or an exercise program, we invariably make a few consistent changes to what we eat, regardless of the instructions we’re given. Specifically, we rid the diet of the most fattening of the carbohydrates,
because these are the easiest to eliminate and the most obviously inappropriate if we’re trying to get in shape. We stop drinking beer, for instance, or at least we drink less, or drink light beer instead. We might think of this as cutting calories, but the calories we’re cutting are carbohydrates, and, more important, they’re liquid, refined carbohydrates, which are exceedingly fattening.

We’ll stop drinking caloric sodas—Coca-Cola, Pepsi, Dr Pepper—and replace them with either water or diet sodas. In doing so, we’re not just removing the liquid carbohydrates that constitute the calories but the fructose, which is specifically responsible for making the sodas sweet. The same is true of fruit juices. An easy change in any diet is to replace fruit juices with water. We’ll get rid of candy bars, desserts, donuts, and cinnamon buns. Again, we’ll perceive this as calorie cutting—and maybe even a way to cut fat, which it can be—but we’re also cutting carbohydrates, specifically fructose. (Even the very low-fat diet made famous by Dean Ornish restricts all refined carbohydrates, including sugar, white rice, and white flour.
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This alone could explain any benefits that result.) Starches like potatoes and rice, refined carbohydrates like bread and pasta, will often be replaced by green vegetables, salads, or at least whole grains, because we’ve been told for the past few decades to eat more fiber and to eat foods that are less energy-dense.

If we try to cut any significant number of calories from our diet, we’ll be cutting the total amount of carbohydrates we consume as well. This is just arithmetic. If we cut all the calories we consume by half, for instance, then we’re cutting the carbohydrates by half, too. And because carbohydrates constitute the largest proportion of calories in our diet, these will see the greatest
absolute reduction. Even if our goal is to cut fat calories, we’ll find it exceedingly difficult to cut more than a few hundred calories a day by reducing fat, and so we’ll have to eat fewer carbohydrates as well. Low-fat diets that also cut calories will cut carbohydrates by as much or more.
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Simply put, any time we try to diet by any of the conventional methods, and any time we decide to “eat healthy” as it’s currently defined, we will remove the most fattening carbohydrates from the diet and some portion of total carbohydrates as well. And if we lose fat, this will almost assuredly be the reason why. (This is the opposite of what happens, by the way, when food producers make low-fat products. They remove a little of the fat and its calories, but then replace it with carbohydrates. In the case of low-fat yogurt, for instance, they replace much of the fat removed with high-fructose corn syrup. We think we’re eating a heart-healthy, low-fat snack that will lead to weight loss. Instead, we get fatter because of the added carbohydrates and fructose.)

The same is likely to be true for those who swear they lost their excess pounds by taking up regular exercise. Rare are the people who begin running or swimming or doing aerobics five times a week to slim down but don’t make any changes in what they eat. Rather, they cut down their beer and soda consumption, reduce
their sweets, and maybe even try to replace starches with green vegetables.

When calorie-restricted diets fail, as they typically do (and the same can be said of exercise programs), the reason is that they restrict something other than the foods that make us fat. They restrict fat and protein, which have no long-term effect on insulin and fat deposition but are required for energy and for the rebuilding of cells and tissues. They starve the entire body of nutrients and energy, or semi-starve it, rather than targeting the fat tissue specifically. Any weight that might be lost can be maintained only as long as the dieter can withstand the semi-starvation, and even then the fat cells will be working to recoup the fat they’re losing, just as the muscle cells are trying to obtain protein to rebuild and maintain their function, and the total amount of energy the dieter expends will be reduced to compensate.

What Adiposity 101 ultimately teaches us is that weight-loss regimens succeed when they get rid of the fattening carbohydrates in the diet; they fail when they don’t. What the regimen must do, in essence, is reregulate fat tissue so that it releases the calories it has accumulated to excess. Any changes the dieter makes that don’t work toward that goal (reducing the fat and protein consumed, in particular) will starve the body in other ways (of energy, and of protein needed to rebuild muscle), and the resultant hunger will lead to failure.

Jean Anthelme Brillat-Savarin was born in 1755. He became first a lawyer and then a politician. His passion, though, was always food and drink, or what he called the “pleasures of the table.” He began writing down his thoughts on the subject in the 1790s; Brillat-Savarin published them in a book,
The Physiology of Taste
, in December 1825. He died of pneumonia two months later, but
The Physiology of Taste
has remained in print ever since. “Tell me what you eat,” Brillat-Savarin memorably wrote, “and I shall tell you what you are.”