TRUE: One Weight-Loss Approach Fits All? No, Not Even Close.

Dr. Frank Sacks, a professor of nutrition at Harvard, likes to challenge his audience when he gives lectures on obesity.

“If you want to make a great discovery,” he tells them, figure out this: Why do some people lose 50 pounds on a diet while others on the same diet gain a few pounds?

Then he shows them data from a study he did that found exactly that effect.

Dr. Sacks’s challenge is a question at the center of obesity research today. Two people can have the same amount of excess weight, they can be the same age, the same socioeconomic class, the same race, the same gender. And yet a treatment that works for one will do nothing for the other.

The problem, researchers say, is that obesity and its precursor — being overweight — are not one disease but instead, like cancer, they are many. “You can look at two people with the same amount of excess body weight and they put on the weight for very different reasons,” said Dr. Arya Sharma, medical director of the obesity program at the University of Alberta.

The more we know about nutrition, weight, and exercise, the less we know in some ways. Though you won’t go far wrong following Gary Taubes and Mark Rippetoe.