Why We Eat

By Jeffrey Kluger; Christine Gorman; Alice Park

FOR SOCIAL REASONS For humans, food does more than merely nourish. It socializes--and civilizes--us as well

If you ever find yourself dining with a family in the South African kingdom of Lesotho, you'd better have a taste for eyeballs--that is, if you're the male head of a household. Tradition requires the host to honor your family in a truly special way: with the cooked head of a sheep. Everyone will be served the feast, but only you will be presented with the eyes.

A sheep's head is a big deal in Lesotho, where most folks don't often get to enjoy meat. When they do, they like it rich and fatty, and they eat it right down to the offal. Presenting the crowning part of so prized a meal to a guest is no small gesture.

For human beings, eating has never been a simple matter. To a frog snagging a fly or a pelican nabbing a fish, food is fuel and nothing more. To a human, the ritual of eating--the act of pulling up and tucking in, of passing around and helping oneself--is one of the most primal of shared activities. We eat together when we celebrate, and we eat together when we grieve; we eat together when a loved one is preparing to leave, and we eat together when the loved one returns. We solve our problems over the family dinner table, conduct our business over the executive lunch table, entertain guests over cake and cookies at the coffee table.

"Interaction over food is the single most important feature of socializing," says Sidney Mintz, professor of anthropology at Johns Hopkins University. "The food becomes the carriage that conveys feelings back and forth."

It's not just families that define themselves through foods. Whole cultures do so too. Muslims eat halal and Jews eat kosher and Roman Catholics forgo meat on Fridays. Moroccans don't eat what Swedes eat, who don't eat what the Japanese eat, who don't eat what Croatians eat. When families leave their home countries and settle elsewhere, the cultural feathering they bring with them--language, dress, music--is often shed within a generation. But the foods linger. "The last part of a culture that gets lost are the food ways," says Barrett Brenton, nutritional anthropologist at St. John's University in New York City. "We find comfort in our cuisines."

Although that has long been the way food works, it is becoming less so--at least in the developed world, where scarcity has been replaced by overabundance and undernourishment by obesity. Increasingly, the connection between eating and ritual is becoming unhinged. We turn too much to food for solace and celebration, and we do it with less and less reference to traditions or even formal mealtimes--to the detriment of our figure and our health.

If the routines we have built around food are complex, it's because we have been working on them for so long. Well before we were very social creatures, we were decidedly hungry creatures, and we ate anything we could lay our hands on. Insects, worms and up to 20 kinds of game were nothing to a hunter-gatherer. As our tastes became more refined, the number of items on our menus shrank, mostly because we did a better job of intuiting what we needed. Cultures that developed a taste for rice and beans didn't know a lick about combining incomplete proteins, but that's what they were doing. People who learned to enjoy high-fiber foods didn't understand intestinal health, but they were helping ensure it nonetheless. "A co-evolutionary process unfolded between cuisines and nourishment," says Brenton. "There's nutritional wisdom behind it all."

How and when we ate became formalized too. When food was scarce, it had to be guarded, so families huddled close to eat what they had caught or picked. Somewhere in there may lie the origins of the dinner table. When food was abundant enough to share, it was passed around mostly at celebrations--harvest festivals, when the foods of autumn were eaten; Easter feasts, when the spring lamb recalled both Jesus' sacrifice and the story of Passover. "The foods became the anchor to which the rituals connected," says Brenton. "You don't see the same foods at a wedding as at a funeral as at a naming ceremony."

All these customs are more than cultural frippery, though we don't always realize it until food and tradition come uncoupled. Among immigrants, particularly those coming to the U.S., the obesity problem has become a full-blown crisis. Even the stubbornest new arrivals may find that their food practices are impossible to maintain in a new environment, where familiar ingredients aren't available, old-world holidays aren't observed and the Mediterranean tradition of the heavy lunch must yield to the less healthy practice of postponing the big meal until the end of the day. "There's a lot of food-related culture shock for new immigrants," says anthropologist David Himmelgreen of the University of South Florida in Tampa.

That discordance can do a lot of damage. Himmelgreen tracked the weight of Puerto Rican women living in the continental U.S. and found that the longer they had been here and the better their English, the more they tended to weigh. "People's food habits change dramatically when they arrive," he says. "The weight gain can happen in a very short time."

For people who have always lived in the U.S., the problem is even worse. There are a lot of reasons for America's obesity epidemic--oversize portions, overprocessed foods, too little exercise. But nutritionists and anthropologists agree that the death of the official mealtime may play the biggest role. "By the time children go to middle school," says anthropologist Marquisa LaVelle of the University of Rhode Island in Kingston, "many families have basically stopped eating together." Solitary eating can be uncontrolled eating--snacks, sweets and meals behind the wheel. "By age 10, everyone in the family can feed themselves whatever they want--and they do," says LaVelle.

Families can change all that. Picking better foods and preparing them healthfully certainly helps. But so does a return to the time when eating was seen not just as a way to fill up but as an opportunity to transact the business of being human. A set table and a balanced meal take a lot more work than a carry-out pizza. But the rewards are infinitely richer.

FOR BIOLOGICAL REASONS Our desire for food--and lots of it--is hardwired into our cells. Do our bodies want to be fat?

There's no question that some pretty strong social, emotional and behavioral forces play a part in determining what, when and how much we eat. But if you really want to know why some people are fat and others aren't, you have to take a good look at biology as well. Mother Nature simply can't afford to leave anything so important to human survival as eating to the whims of cultural fashion. Ten years after the discovery of the first obesity gene, scientists are only beginning to understand just how hardwired our desire for food--and lots of it--truly is.

What they are finding is an exquisitely fine-tuned system of chemical and neurological checks and balances that regulates both what we eat and how much our bodies store as fat. The average American consumes about 1 million calories a year--and, under normal circumstances, burns almost exactly that amount. The body achieves that balance by automatically increasing or decreasing the efficiency with which it performs various tasks, thus consuming fewer or more calories. (Most of the calories we expend are used to breathe, maintain body temperature, keep the brain chugging along, etc. Depending on how much you move, physical activity typically accounts for 15% to 30% of the total.) If you pack on a couple of pounds over the course of the year, your body's error rate is still less than 1%.

Accomplishing that feat requires a lot of communication and coordination among the fat cells, the liver, the muscles, the brain, the stomach and the gastrointestinal tract. Sometimes the signal is a molecule. Other signals are actually conducted along nerve paths. There are even mechanical signals, like the stretching of the stomach, which is one way the body says, "I'm full."

As if all that weren't complicated enough, the body must also regulate its food intake and manage its weight over time. "There are short-term signals and long-term signals," says Judith Korner, an endocrinologist at Columbia University in New York City. "Some signals are both short term and long term, and then there are medium-term signals."

As you might expect, the short-term signals are involved mostly with the initiation and completion of meals. Ghrelin, a hormone produced by the stomach, tells the brain, "It's time to eat!" When enough food leaves the stomach and reaches the small intestine, another hormone, called cholecystokinin, signals that the meal is over--and triggers the release of enzymes in the gallbladder and the pancreas.

The hormones leptin and insulin are longer-term signals. Produced by fat cells, leptin helps manage just how much fat you store around your organs and under your skin through a complex feedback loop. If your fat deposits start to shrink--for example, when you lose weight--the amount of leptin in your body falls, a situation that the brain interprets as a result of starvation. The whole system of chemicals and neurological impulses shifts in an attempt to get the body to burn fewer calories so that it can regain the weight. The greater the weight loss, the stronger the signals to eat more and replenish fat stores.

There are many other factors that affect this delicate balance. For example, laboratory evidence suggests that a diet that boosts your triglycerides--typically, one high in fatty, fried or highly refined foods--may interfere with both leptin's and insulin's actions on the brain, leading to an erroneous signal that the body is in danger of starving. The same receptors in the brain that are responsible for a marijuana high also boost appetite, which is why pot smokers get the munchies.

The more scientists learn about these biochemical, neurological and dietary factors, the more they marvel that anyone in our culture manages to stay thin, given the abundance and easy availability of food. If there's some kind of biological mechanism that protects certain people against weight gain, researchers haven't discovered it. By contrast, the evidence in favor of one that protects against weight loss is increasingly strong. Genetic variations clearly push some people toward bigger appetites, slower metabolisms and greater weight gain than others. "There are genes in the population that predispose to obesity," says Dr. Jeffrey Friedman, a molecular geneticist at the Rockefeller University in New York. "Obviously, there's an environmental contribution, but no one questions that genes are involved."

So the next time you stare in judgment at a fat person on the bus or bemoan your physique in the mirror, remember that nature has stacked the deck against weight loss. Trimming 25 lbs. from your figure may not be that difficult. But try shedding 100 lbs., and your body is going to scream. Whether willpower, exercise, drugs or even surgery is enough to quiet the body's basic need for fat is still an open question.

FOR PSYCHOLOGICAL REASONS What deep inner urges drive some people to overeat and others to starve themselves?

Sometimes in order to fully understand a problem you have to study its opposite. That's why researchers trying to figure out what makes some of us so prone to obesity are taking a close look at patients at the other end of the bathroom scale: anorexics who starve themselves and bulimics who binge and purge. Could over-and undereating, scientists wonder, be two sides of the same coin, different forms of the same biological circuitry gone awry?

Although anorexia and obesity look nothing alike in clinical terms, there are similarities. People with both disorders tend to organize their days around eating and allow food to loom too large in their lives. "People who are anorexic and people who are overweight often begin to get phobic about food," says Dr. William Davis, of the Renfrew Center in Philadelphia, which treats patients with eating disorders. Food for them is much more than a source of nourishment; it can become a substitute for self-esteem and a vehicle for exercising--or losing--control over the body.

But scientists who have studied both groups say that underneath these similarities are two very different syndromes. "Obesity is at its base a metabolic disorder," says Dr. Lee Kaplan, director of the Obesity Research Center at Massachusetts General Hospital. Anorexia and bulimia, he maintains, "are primary psychiatric disorders."

The human body is designed to eat, and eating stops under normal circumstances only when the body senses it has enough energy for its immediate needs and enough stored away for future tasks. "It's hard to lose weight because the body wants to gain it back," says Kaplan. "In a competition between willpower and the body, the body always wins."

Except when an eating disorder has hijacked the process. Anorexics and bulimics are more successful at losing weight than people on diets because they have managed to throw this basic drive to eat into reverse. Through sheer force of will, anorexics convince their body that it doesn't need food. "Anorexics are able to do things that are clearly beyond what a normal person is capable of doing," says Kaplan. "Theirs is extreme behavior often driven by an inappropriate and distorted body image."

By contrast, people who gain weight are following the body's natural urge to hoard calories. Slight changes in the way you burn and store calories can lead, over time, to piling on the pounds. And while some of the factors responsible for these changes are within your control--how much you exercise or whether you take a second helping of ice cream--most are either inherited or the inbred responses of an organism that is designed to protect itself from starvation. Stress, sleep deprivation and long days packed with constant activity have a tendency to accumulate weight. "If we took away cars and television and computers, and stopped eating fast food, but were still exposed to the other stresses of modern life, I don't think we would eliminate obesity," says Kaplan. "We might dampen it, but we wouldn't eliminate it altogether."

And that's why treatments for obesity differ so much from those for anorexics. People who starve themselves tend to respond better to therapies and behavior-modification approaches that address their distorted body image and underlying emotional issues. People with overeating problems are often successfully treated with a more physiological approach, usually through diet and exercise and, sometimes, medications that curb appetite or burn calories more efficiently.