Willpower

consistently come out of prison fatter than when they went in. The reason, according to Cornell’s Brian Wansink, is that prisoners don’t wear belts or tight-fitting clothes. In their jumpsuits and loose pants, they don’t get the little signals of weight gain that other people get when their pants feel tighter and their belts have to be loosened a notch.
    Besides monitoring your body, you can monitor what food you put into it. If you conscientiously keep a record of all the food you eat, you’ll probably consume fewer calories. In one study, those who kept a food diary lost twice as much weight as those who used other techniques. It also helps to record how many calories are in the food, although that’s notoriously tricky to estimate. All of us, even professional dietitians, tend to underestimate how much food is on a plate, especially when confronted with large portions. We’ve been further confused by the warnings of nutritionists and the tricks of food companies, who will use a label like “low-fat” or “organic” to create what researchers call a “health halo.” Tierney investigated this phenomenon in the nutritionally correct neighborhood of Park Slope, Brooklyn, with an experiment designed by two researchers, Pierre Chandon and Alexander Chernev. Some of the Park Slopers were shown pictures of an Applebee’s meal consisting of chicken salad and a Pepsi; others were shown the identical meal plus some crackers prominently labeled “Trans Fat Free.” The people were so entranced by the crackers’ virtuous label that their estimate for the meal with crackers was lower than for the same meal without crackers. The label magically translated into “negative calories,” both in the informal experiment in Park Slope and in a formal peer-reviewed study published later by Chernev. Other studies have shown that both laypeople and nutritional experts consistently underestimate the calories in food labeled “low-fat,” and consequently take bigger helpings.
    To overcome these problems, you can try paying more attention to the calorie count of food when it’s available on a label or a menu, or when you’ve got a smartphone with an app that monitors calories. When the calorie count is not available, you can at least try to pay attention to the food in front of you, which few people do. The two most common activities that are combined with eating are socializing and watching television—and both are associated with increased calorie consumption. Researchers have repeatedly shown that eating in front of the television increases snacking, and that viewers will eat more when their attention is engaged—as in a well-executed comedy or horror film—than when they’re watching something boring. In one study, female dieters tripled the amount of food they ate when they were absorbed in a film.
    People tend to eat more at meals with friends and family, when they’re paying more attention to the company and less to what they eat. Add wine or beer, and they’ll pay still less attention, because alcohol reduces self-awareness and therefore impairs monitoring. Even when they’re sober, diners can be so oblivious that they’ll go on sipping soup from a bowl that is continuously (and surreptitiously) refilled, as Brian Wansink demonstrated in a famous experiment at Cornell using soup bowls attached to hidden tubes. The people just went on sipping from the bottomless bowl because they were so used to eating whatever was put in front of them. If you’re guided by external cues instead of by your own appetite, you’re vulnerable to gaining weight whenever you’re served large portions, which can easily happen without your being aware of it. When food is served on large plates or when drinks are poured in wide glasses, you tend to underestimate how many extra calories are being added because you don’t have a good intuitive sense of three-dimensional volume. If a movie theater simply changed one dimension of a popcorn bag by, say, tripling its height, you could see right away that it holds three times as much popcorn. But when the bag gets simultaneously wider, deeper, and taller, it can triple in volume without looking three times as big. So you order the large—and then eat the whole thing. You can’t control what kind of packaging and plates are used in theaters and restaurants, but at home you can reduce your portions by using small plates and thin glasses.
    You can also make it easier to monitor your