Why We Eat When We're Not Hungry

A bell rings; a dog drools. This is the oldest trick in the Psychology 101 book: That’s all it takes for the pooch to expect something to eat. Dumb dogs! The poor suckers.... Oh, wait. We humans are just as nefariously conditioned to eat when we’re not hungry. Which might explain the staggering tally of calories you ingest some days but don’t especially remember (or savor). But scientists have been investigating common triggers that cause overeating and keep people from shedding the extra pounds that dog them — and their findings suggest how we can bring those urges to heel.

The ‘I’ll have what she’s having’ effect

Who doesn’t want to be just like her thinnest friend, with her XS shirts and size 26 jeans (a waist size last seen by most of us during sixth grade)? The problem is, though, that we tend to emulate her when she’s stuffing herself and trying to fill her hollow leg. In a joint study at Duke University, the University of British Columbia, and Arizona State University, an undercover researcher — a size 0 woman, either dressed normally or in a size 16 fat suit — ordered food in front of a study participant. In all cases, the participants made similar orders to the researcher’s. But she had the most influence when she looked thin: When she ate more, her companions ate more.

This study is the latest arrival at a crowded buffet table of research about peer-induced overeating. For instance, as your number of dining partners increases, so does your caloric intake; one study found that eating with eight others can prompt you to consume nearly double the calories you would when alone.

One mitigating factor is that women rein themselves in when a man dines with them, a 2009 study at McMaster University in Ontario, Canada, found. Notably, the men were unrelated to the women in the test: Once women get married or start living with a man, they tend to weigh more, research shows. Plus, the heavier one’s friends, the higher one’s own chances of becoming overweight, according to analysis by scientists at Harvard University and the University of San Diego. “When people around you gain weight, how is that transmitted to you? By sharing behavior,” says Nicholas Christakis, a physician and sociologist at Harvard who explores this phenomenon in “Connected” (Little, Brown and Company). “It’s either ‘Let’s go running’ or ‘Let’s share these muffins.’”

In the cinematic “Sex and the City 2” world, venues for female camaraderie might include a Bergdorf dressing room or a spalike desert oasis. In the real world, though, women’s friendships more often take place at restaurant tables, usually strewn with quarter-full wine glasses and the empty plates of multicourse meals. This ritual will likely never change (nor should it — even the most spirited Facebook comment threads can’t hold a candle), but it can be controlled. It may be as simple as everyone meeting for a drink after having had dinner separately. “If you’re already full when you walk into a restaurant, it’s much easier to avoid overeating,” says Susan Roberts, author of “The ‘I’ Diet” (Workman) and professor of nutrition at Tufts University in Boston. You could also just invite a cute single guy along, given that, as prefeminist as it is, women tend to eat fewer calories when they’re in the company of men, “even when it’s not a dating situation,” says Lauren Slayton, a nutritionist in New York City and founder of foodtrainers.net. “Also, women like to talk, and as long as there’s food in front of you, you’ll keep eating.” So ask the waiter to clear any plates — but leave the water glasses — as soon as possible.

The couch (sour cream-topped, butter-slathered) potato effect

This might seem as fresh and new as watching the same “Law & Order: Special Victims Unit” episode for the millionth time, but bear with the repeat: TV viewing can make you fat. A recent study at Yale University found that TV viewers who saw snack commercials were inspired to eat — paging Don Draper! — just about anything, not just the brand advertised. Plus, the snacking was completely unrelated to feeling either hungry beforehand or full afterward.

When study subjects watched television for a half-hour, they consumed 36 percent more calories of pizza, or 71 percent more calories of macaroni and cheese, compared with people who listened to music for a half-hour, according to a 2006 article in Physiology and Behavior. (Listening to music has been linked with higher food intake in other research, so presumably all these study subjects ate more than they would have with no distractions at all.) Successful dieters, meanwhile, tend to watch far less television than the average adult’s four hours a day: The majority of people in the National Weight Control Registry, a group of about 5,000 people who’ve kept off at least 30 pounds, average fewer than ten hours of TV a week.

“If you separate eating from TV viewing, you will probably be thin,” Roberts says. But if you can’t resist snacking in front of the screen, have “vegetables and a yogurt-based dip, so you can put something in your mouth that doesn’t do damage.” Staring at a computer can present an overeating hazard as well, which is why Slayton advises against emailing during lunch at work. She also suggests a “TV diet” to go with your food diet: “If you keep track of how much you eat and how much you work out, you should also log how much time you spend watching TV, because it’s another variable,” she says. People who watched half as much TV as usual for three weeks burned an extra 119 calories per day — comparable to the effect of walking more than a mile, a recent study in Archives of Internal Medicine found. As a rule, Slayton tells her clients to watch just one hour a day. She does offer dispensation, though, for TV viewing while using cardio equipment: “I don’t care how many ‘Housewives’ episodes you watch as long as you’re on the treadmill.”

The Snackwell effect

So-called diet foods can sabotage the best weight-loss intentions — presumably because people think they’re free passes to indulge. For weight-conscious people, portion-controlled snack bags seem to fail miserably at actually controlling portions, a study at Tilburg University in the Netherlands found: Given the option of two large bags of chips or nine snack-size bags, 59 percent of the participants chose smaller bags — but ate twice as much as those who went for the large bags. Even the mention of salad on a menu, it turns out, can paradoxically inspire the least healthy meal choices among people who usually have the most self-control. A study at Duke University presented people with one menu that offered a buttered baked potato (considered the healthiest choice), chicken nuggets, or French fries. A second menu listed those items as well as a side salad. When that plate of greens was on offer, nearly three times as many people ordered the fries. Moreover, the participants who generally made a point of watching their intake were most likely to switch their order from the potato to the fries. The researchers theorize that the mere option of eating healthy makes diners feel as if they’ve achieved a goal, so they reward themselves for that with the indulgent choice.

Some diet foods are “truly self-limiting,” Roberts points out, “like Fiber One cereal.” Or kale. Or celery sticks. Or anything with a high water or fiber content, or both. With the stuff that actually tastes good, meanwhile, you still need to pay attention to portion size. “People fool themselves into thinking they’re having 50 calories when it’s really 200,” says Jennifer Warren of the Physicians Healthy Weight Center in North Hampton, New Hampshire. She points out that including lean protein, such as an egg or a piece of chicken, at breakfast and lunch can keep you from becoming ravenous between meals.

The surprising salad effect

As for fattening salads — and not just those that go by the names of Cobb or Caesar — there might also be some warped dieter’s psychology involved: If you always get a salad, and don’t give yourself the option of anything else, the caloric count will creep up as you try to sneak in an appetizing break from monotony. “Perpetual dieters need to learn how to waver from the plan,” Slayton says. “If you order the lentil soup and salad and end up eating the bread and crackers and getting fries ‘for the table,’ you’d be better off just ordering a sandwich to begin with.”

If you do get the salad, remember to exercise some restraint, especially at those you-boss-they-toss salad bars. “Try lots of dark greens; ample lean protein such as shrimp, plain tuna, or beans; three or four unadulterated vegetables; and one treat ingredient such as nuts, cheese, bacon, olives, avocado, croutons, or dried fruit,” Slayton says. Get the dressing on the side, too, since olive oil, healthy fat though it is, still has 120 calories per tablespoon.

The fattening room effect

You are what you eat — and you eat what you are seeing, smelling, or contemplating. “The sight, smell, and talk of food trigger real metabolic signals of hunger,” Roberts notes, “even when your stomach is full.” (In fact, proximity to fast-food outlets is linked with weight gain and obesity, according to a vast study of teenagers conducted by Columbia University and the University of California.) But the appetite is also influenced by more subliminal aspects of one’s surroundings. In a study at the University of Illinois in Champaign, people who were exposed to posters touting an exercise program ate 54 percent more calories than those exposed to posters without a workout theme; similarly, participants wanted to eat after reading sporty words like “active.” Moreover, settings with glaring light and those with soft candlelight can both contribute to overconsumption, since the former can prompt people to eat faster and the latter can cause them to linger and eat longer.

Given the relentlessness of findings that suggest that just about everything can lead to weight gain, it makes sense that your instinct might be to go bury your head in the sand (or a box of pecan sandies). Indeed, turning away from seductive images of food can help reduce hunger, Roberts says. If you live with people who insist on having junk food in the house, Warren advises keeping it on a high shelf. Double-bag ice cream in the freezer so you can’t see it when you open the door, and if you do feel its pull, you can keep your mouth busy with a Listerine breath strip or a sugar-free cough lozenge.

Maybe the most helpful adjustment, however, would be to your thinking. As Slayton says, “People don’t reach their weight-loss goals simply because they focus on what they eat. They also look at the external factors that make them overeat and use them to their favor.”

-Rory Evans

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