Why Diets Make Us Fat The Unintended Consequences of Our Obsession With Weight Loss

Why Diets Make Us Fat The Unintended Consequences of Our Obsession With Weight Loss

several years ago, my husband and I visited friends who had two teenage daughters. Both girls were smart, beautiful, and well loved, but only one was thin. Her sister had started gaining weight at puberty, and their parents couldn’t figure out what to do. They’d tried talking to her about portion control and exercise. They’d tried cooking her special food. Nothing slowed her progression from skinny child to voluptuous woman.

Their well-meaning concern was making the situation worse. She was reluctant to sit down for meals with the family—and ate almost nothing when she did. But her father told me that food was disappearing from the refrigerator in the middle of the night, and her weight gain continued. Rather than making her thin, her parents’ anxiety was pushing her toward an eating disorder and increasing her odds of gaining more weight.

I understood her feelings because I was that teenage girl myself several decades ago, hating myself because I couldn’t satisfy my culture’s expectations for my body. Because I grew up to be a neuroscientist, I also knew about the biology behind her struggles. Considerable evidence shows that dieting—willfully eating less to lose weight—rarely works in the long run, while its unintended side effects do a lot of harm.

Part One: The Trouble with Diets

is oldest daughter’s wedding was the final straw. Dennis Asbury could avoid looking in mirrors, but he couldn’t ask his wife not to hang photos from the celebration on the wall. The truth was staring at him: at age forty-five, he carried 283 pounds on his 5’9” frame and had a fifty-two-inch waist. Stress at his job as director of environmental services for the town of Eden, North Carolina, had led him to overeat for years. Now the bill had come due. 

The next week at a checkup, he asked his doctor for help with weight loss. Like six million other people in the United States, he took home a prescription for fenfluramine-phentermine, better known as fen-phen.1 The drug combination was everywhere in 1996, after a strong marketing push from its manufacturer, American Home Products, based on a four-year study of only 121 patients.

For Dennis, the drugs were a revelation. After taking one pill, he felt like he was in someone else’s body. For the first time in years, he could get through an entire thought at work without anticipating his next meal. Encouraged, he plunged into his diet with enthusiasm.

As a numbers guy, Dennis approached his new lifestyle with the spirit of an engineer, logging every bite of food and each minute of exercise. If he did the math correctly, he believed, everything else would work out, whether the problem was a city budget or a calorie budget. He gave up all the foods he loved and tried to move as much as possible, often waking at three a.m. to walk the streets. “Fortunately, I worked for the city,” he says, “and most of the police officers knew me.” 

In the evening, he walked at least another hour and then lifted weights. Instead of following a specific diet, he tried to keep his calorie intake as low as possible, sometimes managing to hit six hundred calories for several days in a row. In six months, he had reached 160 pounds. He was thrilled, and so were his wife and his doctor, who took him off the drugs in the spring of 1997. The hard part was over, Dennis thought, although he planned to keep tracking his calories and exercise for life to avoid regaining the weight.

By losing so much weight through diet and exercise, Dennis had already beaten long odds. Men in his starting weight range have only a 1-in-1,290 chance per year of reaching the normal range. Yet keeping the weight off proved even more difficult, as the research predicts. Abundant scientific evidence indicates that almost everyone who loses a lot of weight ends up gaining it back in the long run. That’s not because dieters are lazy or lack willpower. Instead the culprit is biology: in particular, the brain’s ability to fight back against weight loss.

The Defended Weight Range

The brain has powerful ways of defending the body weight that is its target. This target, often called the set point, is really a range, spanning about ten or fifteen pounds. Within this range, weight is relatively easy to modify through lifestyle changes, while staying below the brain’s target is difficult. Over time, the defended range can change—but it goes up much more easily than it goes down.

This imbalance means that weight gain is often not reversible. People are likely to be thinner in the long run if they focus on keeping their brain’s defended weight range from increasing in the first place than if they rely on losing weight after they’ve kept it on for a while.

The brain’s weight-regulation system has two simple priorities: body weight should remain stable and shouldn’t decrease too much. Both these goals were sensible for most of human history (starvation is a much worse fate than obesity), but in modern life, with high-calorie food so easy to find, the second priority has become a problem for many people. Efforts to defeat the brain’s resistance to weight loss often end up increasing the influence of external cues like advertising that promote overeating. 

When people are obese, it’s usually because their brain considers that weight to be correct for them. If someone started at 120 pounds and dieted down to 80 pounds, her brain would declare a starvation state of emergency, using every method available to get her weight back up to normal—and exactly the same thing would happen to someone who started at 300 pounds and lost down to 200 pounds.

Although we often assume that the brain should know the difference between a normal-weight person and an obese person when it comesto weight loss, considerable evidence indicates that the brain doesn’t distinguish the two situations.

Part Two: Why We Gain Weight

Early Life and Adult Weight

he winter of 1944–45 was unusually cold in northern Europe, but the news was good. The Allied armies rapidly gained ground, and the war seemed likely to end soon. In September and October, soldiers liberated the southern provinces of the Netherlands from a Nazi occupation that had begun in 1940. To support the Allied attack, the Dutch government-in-exile called for a railway strike, and thirty thousand workers complied. An attempted airborne landing failed to free the western provinces, though, as the German army used its own trains to bring in troops, and the Allies moved on toward Berlin.

In retaliation for the Dutch resistance, a German blockade prevented the delivery of supplies to the parts of the country that remained under Nazi control, so civilians had to scrap for calories and heat any way they could manage. Rations dropped from 1,200 calories per day in November to 800 in January to fewer than 600 in February, mostly bread and potatoes.

Earlier in the war, pregnant and nursing mothers had gotten supplemental rations, but by late fall there was not enough food available to continue them. People burned furniture and ate tulip bulbs. Farmers put up signs saying that they would no longer trade food for the fancy linens of the city folk. More than twenty thousand people died between November 1944 and May 1945, and everyone starved. 

The biological consequences of the Dutch Hunger Winter would echo through the rest of the survivors’ lives, their children’s lives, and in some cases their grandchildren’s lives. These war victims contributed a great deal to our understanding of the lasting effects of early life experience. Centralized health care and excellent record keeping allowed researchers to study the long-term effects of a single period of malnutrition of known length and timing during an otherwise adequately fed lifetime. 

They found that a baby’s nutrition in the womb had lifelong effects on weight.1 When women starved in the last few months ofpregnancy, their babies were born small and remained small and thin for the rest of their lives, despite having access to normal amounts of food. The grandchildren of these women also had low birth weights.

In contrast, if women starved in the first half of their pregnancies and then ate well, their babies had normal birth weights but were heavier as adults. When mothers starved early in gestation, their daughters (but not sons) had strong odds of increased weight and waist circumference as adults. These women were also more susceptible to diabetes, regardless of their adult weight. 

The same pattern was found in women whose mothers were pregnant during the massive famine caused by Mao’s Great Leap Forward in China, compared with those born in areas where food remained available. No one knows for sure why male babies are less affected by early starvation, but one possibility is that weight regulation is more important for women because it affects their fertility.

Pregnancy Prepares Babies for Their World

A relationship between the conditions during fetal development and adult characteristics makes sense if we think about pregnancy as an opportunity to match each baby to the external environment in which he or she will live.3 In people and other animals, biology uses information from the environment to shape the growth of babies before they’re born. If food is scarce out there, a smaller, thinner body will make it easier to get enough to eat. Tastes from the mother’s diet that reach the baby’s tongue in the womb signal what is safe to eat around here and shape the child’s later food preferences. 

If danger lurks all around, a hair-trigger stress system that reacts to any hint of trouble may be necessary for survival, so the health costs of long-term stress could be worth paying. If conditions are welcoming, though, then people will be most successful if they take advantage of the abundant resources to grow big and strong, rather than wasting energy jumping at shadows. 

When the mother’s environment during pregnancy correctly predicts the world that the baby will live in, then this developmental plasticity makes the baby more successful. Problems can result, though—either because of inherent trade-offs, as in stress responsiveness, or because the adult ends up in an environment that doesn’t match the one to which its young body was adapted.

Stressed Children Become Heavy Adults

Another early-life experience that increases the odds of adult obesity is severe childhood stress, which can be caused by poverty or abuse. In many species, including people, early life stress permanently makes the stress response system more reactive, which helps animals survive in a threatening environment. The brain changes caused by early stress make stress hormone responses easier to activate and harder to turn off. One cause of this exaggerated response is a decline in the number of stress hormone receptors available to receive the feedback that shuts the response down. 

The biological basis for these changes is well understood from research in rodents and monkeys, and the broad outlines appear similar in people. The persistent stress hormone exposure resulting from this hypersensitive stress system has serious drawbacks. It increases vulnerability to abdominal obesity and both physical and mental health problems. For people who grow up in a war zone, where extreme vigilance is needed just to get through the day, those trade-offs may be worth it, but the price is high.

Maternal Smoking and Weight

Although nicotine suppresses appetite in the short term, nicotine exposure before birth can increase the long-term odds of obesity. Strong evidence suggests that babies whose mothers smoked during pregnancy are 50 percent more likely to become obese later in life. Since public health campaigns have reduced smoking over the past few decades, women who smoke while pregnant now differ from women who don’t, which complicates the interpretation of studies. Pregnant smokers are poorer, less educated, heavier themselves, and less likely to breast-feed, which are all qualities that predict childhood obesity. 

Yet adjusting statistically for these characteristics does not remove the risk posed by smoking. Similar risks were found in older U.S. studies and in European studies, in which smokers were less different from the rest of society. In addition, mothers who smoke after pregnancy do not increase their children’s odds of obesity, although they are similar to women who smoke during pregnancy.

Finally, this association is supported by laboratory animal studies, which find that prenatal nicotine leads to lower birth weight and increased body fat later in life. For all those reasons, the association between smoking during pregnancy and later obesity is probably real.

Part Three: A Better Way

Eat with Attention and Joy

ordon Rosenberg, an eighty-nine-year-old walnut farmer, had come to learn mindful eating at the Esalen Institute in Big Sur, California—famed for its meditating hippies and hot springs overlooking the Pacific. So far, he was finding it difficult to tune in to his body’s signals. “I’m never hungry,” he whispered to his wife, Vicky. Instead, as a “charter member of the Clean Plate Society,” he ate whenever food was in front of him. He had trouble holding on to snacks long enough to listen to the instructions for mindful-eating exercises.

Hounded by voices from his Depression-era childhood, he proudly ate the core and seeds of his apples, and he never threw leftovers away. At its heart, mindful eating means making conscious choices about what to eat. The focus is on aligning our bodies’ needs with our values, instead of giving up control to rules, habits, or external cues that don’t support our goals. By giving ourselves permission to savor whatever food we want at that moment, without guilt, we can be fully satisfied after we eat. This approach allows us to get more pleasure from food, while eating exactly the amount we want, and so bring the brain’s reward and energy-balance systems into alignment.

The only way to learn how to do that is to “play with your food,” as workshop leader Jean Kristeller put it, by experimenting with different eating patterns and observing the results with curiosity and kindness. Gordon’s intense need to eat everything on his plate interfered with his experiments. Other workshop participants suggested alternatives to wasting the unwanted food, from giving it to a local homeless person to sending an equivalent donation to a famine relief organization, but Gordon was unmoved. By the end of the weekend, with great effort, he had managed to leave a single bite of food on his plate.

Your Brain Knows How Much to Eat

Rigid food rules train us to ignore hunger, which reduces the influence of the energy-balance system. Mindfulness provides a set of techniques that help us to get back in touch with our bodies, as we let the voices in our heads flow by without undue influence on behavior. Strengthening the body signals from hunger and satiety gives the brain’s energy-balance system more influence over eating. 

By relying on this system, which never takes any time off from work, we’re protected against overeating in the inevitable moments when willpower fails. People with a strong disposition toward being mindful of their physical and emotional experiences are less likely to have disordered eating behaviors, are less likely to act on eating-disordered thoughts, are thinner, are more physically active, and have better cardiovascular health in middle age.

Mindfulness combines deliberate attention to the present moment with acceptance of the world exactly as it is. Both aspects are necessary, and most people find both to be challenging, at least at first. Acceptance doesn’t mean the belief that the situation is the best it could possibly be. Instead it’s the deep realization that this is the only reality that exists right now, so it makes sense to live in it without trying to push it away. 

Though these skills are often practiced during formal meditation sessions, they can also be learned as part of daily life. I didn’t manage to stick to a formal mindfulness practice on a regular schedule until several years after I started paying attention to hunger cues informally.

Listening to the Body

The idea that it’s psychologically and physically healthier to eat in response to internal cues than to count calories goes back to the antidieting movement of the 1970s and 1980s. As eating disorders and routine temptations to overeat became increasingly common, many women realized that restrictive diets caused more problems than they solved and started looking for a better way. 

Dietitians Evelyn Tribole and Elyse Resch describe this approach as “intuitive eating” in their book of the same name. They define intuitive eaters as people who give themselves permission to eat whatever they want when they’re hungry, eat in response to hunger and satiety, and don’t eat for emotionalreasons. Mindful eating differs from intuitive eating mostly in the set of techniques that are used to develop this ability.

From middle school to middle age, intuitive eaters weigh less than their peers and are protected against weight gain.Intuitive eaters enjoy preparing and eating food more, and although they are less health conscious, they eat a more varied diet. They are less likely to binge and more likely to exercise because it feels good. One small study found that intuitive eaters have lower triglycerides and higher HDL (good) cholesterol compared with eaters who ignore internal cues. 

Intuitive eaters also have fewer symptoms of eating disorders, are less depressed, have higher self-esteem, feel less pressure to be thin, and do not value thinness as an ideal body shape. In contrast to the temporary effectiveness of dieting, which leads to worse results as time goes on, intuitive eating studies produce better outcomes with longer follow-up.

How to Eat Mindfully

A few tactics can help you learn to become a more mindful eater. Begin meals at a moderate level of hunger because people who are starving tend to eat too fast, which makes it hard to tell when they’re full before they’re overstuffed. Along the same lines, try to eat more slowly than usual, which also provides more taste sensations. If possible, create a space to eat without distractions, at least for some meals and snacks. If an entire mindful meal is too much to manage, consider starting to eat with a brief silent ritual of tasting the first bite of each food carefully, experiencing its appearance, smells, flavors, and textures with gratitude. 

Pay attention to the way the body feels before eating, stop in the middle of each meal to check on hunger, and note how the body feels after eating. If the answer is that it feels stuffed and uncomfortable, congratulations—that’s an important lesson about how to feel better next time. The more different kinds of food and eating patterns that we try, the more information we have to decide what we want to eat.

During the learning process, some people find it helpful to take notes on their feelings, while others rely more on their accumulated experience. The note-taking types might try rating hunger on a scale of one to ten before and after they eat. They might also want to record what they ate, the emotions they were feeling, how satisfied they felt after eating, and any environmental situations that seem relevant, such as being in a restaurant or eating while distracted. Looking back over these notes can sometimes help people to see patterns that weren’t clear at the time. There’s no need to keep notes on food quantities, especially if that tactic draws the focus back to weight loss, as it does for many recovering dieters.

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