The Calculus Diaries - Jennifer Ouellette [75]
Even the most chronic yo-yo dieter can recite the mantra. If you don’t take in sufficient calories to give your body the energy it needs, it will begin converting fat cells into fuel—and you will lose weight. The converse is also true: If you consume more calories than your body needs, it will store that excess energy as fat. Stored fat is another fuel source for the body,46 just like the food you consume. There are 3,500 calories in a pound of body fat, so it is possible to reduce one’s daily caloric intake by 250 calories, burn off an extra 250 calories with daily exercise, and thus lose a pound per week.
So why is obesity so prevalent in our society? There are myriad rationales being bandied about, but from a thermodynamics standpoint, it is very simple: We are heavier than people in many other societies because we routinely consume more calories than we need for our bodies to function. This is difficult for many people to accept; they will claim they really don’t eat all that much and insist they must have a slow metabolism. Individual metabolic rates do indeed vary widely—and the Harris-Benedict equation takes this variation into account—as do body types, and no doubt genetics plays a role as well in determining one’s natural, healthy weight.
Those arguments don’t change the fundamental principle: People with lower metabolic rates need fewer calories. When they consume more calories than their bodies require—even if they eat less than “naturally” slim colleagues—they gain weight. It hardly seems fair. But who said physics was fair? Frankly, in times of famine, a low metabolism confers a distinct evolutionary advantage because it can do more with a small amount of fuel. It’s when food is plentiful that this superefficiency becomes a disadvantage.47
Psychologically, we easily can trick ourselves into thinking we eat less than we really do. Studies have shown that the vast majority of us routinely underestimate how many calories we consume. (It doesn’t take much to hit 2,000 calories, particularly if one is partial to fast food.) Brian Wansink is a professor at Cornell University who specializes in the study of consumer behavior and nutritional science, specifically how our environment influences our eating habits. In 2007, he and his colleague, Pierre Chandon, published the results of a study in the Journal of Consumer Research, demonstrating that people have become so conditioned to think that the Subway franchise’s food is healthier than McDonald’s that they underestimate how many calories they consume in a typical meal by as much as 21 percent. Famed Subway spokesman Jared may have lost a ton of weight by eating the chain’s sandwiches, but he chose the healthier options. A Subway twelve-inch Italian BMT sandwich has one third more calories than a McDonald’s Big Mac. Wansink and Chandon also found that people tended to choose high-calorie side orders with their Subway sandwiches.
For one of his earliest research studies, Wansink focused on automatic eating patterns. People would come to the lab and eat a meal while being videotaped, then answer questions about what and how much they ate. He found that people were often unaware of second or even third helpings they consumed and denied doing so—until they were shown the videotape. Other interesting findings: People will eat 16 to 23 percent more total calories if a product is stamped with a LOW-FAT label, and switching from a twelve-inch to a ten-inch dinner plate will cause people to eat 22 percent less. All this inspired Wansink to develop his own dietary secret: “The best diet is the one you don’t know you’re on.” In other words, small changes to the home environment and unconscious