Just the other day, Michael ate a salad and two large helpings of spaghetti and meatballs for dinner — after having a hearty bowl of ice cream. For breakfast the next morning, she ate two scrambled eggs, half a package of Polish sausage, English muffins and orange juice. For lunch, she consumed a 12-inch seafood sub and some Doritos, and that night’s dinner featured two pork chops, potatoes and broccoli.
That Michael’s weight remains steady even though she eats whatever she wants and does not exercise interests scientists studying the nation’s obesity epidemic. By looking at people who are near their ideal body weight, these reseachers at the National Institutes of Health’s Metabolic Clinical Research Unit in Bethesda hope to figure out what causes so many others to be overweight or uncontrollably fat.
Michael is among the one-third of American adults who are at a good weight relative to their height and build. Another third are overweight, and the rest are obese. Unlike Michael, very few people keep their weight in check without paying attention to what they eat and being conscientious about physical activity.
For years, people have been told to diet, control their appetites, use a little willpower. But more and more scientists believe the obesity epidemic has been triggered by a combination beyond an individual’s control: genes, and how they interact with an environment of abundant, tasty, inexpensive and hard-to-resist food.
Each person’s unique genetic makeup, these experts think, may affect what he craves, how much he craves and how his body uses fat and burns calories.
“We are hard-wired to be a bit more hungry than we need to, because until very recently — in evolutionary terms — the vast majority of our fellow humans had no idea whether the next meal would be available or not,” said Francesco S. Celi, a clinical investigator at the NIH research unit.
Yet for some people, there is a profound imbalance between what they eat and the amount of energy they expend. Most of these people become obese as a result, but some, like Michael, don’t.
“Some are more sensitive” to that imbalance, said Rudolph Leibel, a diabetes researcher at New York’s Columbia University who has been studying the biochemistry and genetics of obesity for 25 years. “That’s the genetics.”
“There are people in the population who are skinnier or more slender with a different genetic response to the environment,” he said. That is why “just yelling at people and telling them it is sinful or gluttony is not a particular fruitful way to deal with the problem. It’s not very effective to insinuate that someone has moral failings when a behavior is involved.”