Study Offers the Obese Food for Thought: It’s Caloric, Not Genetic

Everyone has heard the lament: I eat like a bird, but I can’t lose weight.

Now, however, a study by doctors concludes that many obese people who blame their genes or their metabolisms actually fail to lose weight because they eat too much.

The researchers said those who claim that they simply cannot take off pounds may be fooling themselves: They eat far more--and exercise less--than they think.

Doctors from St. Luke’s-Roosevelt Hospital Center in New York set up the experiment after repeatedly hearing stories from overweight patients who claimed they simply could not slim down, no matter what.

The researchers carefully followed obese people who had failed as many as 20 diets and claimed to eat less than 1,200 calories a day.

“There were two alternatives--low metabolism and under-reporting of food intake. Both hypotheses seemed plausible to us,” said Dr. Steven B. Heymsfield, medical director of the hospital’s weight control unit.

It turned out that their metabolisms were completely normal. The problem was that they were eating twice as much as they thought they were.

Of course, metabolism contributes to obesity. So does genetic inheritance. But the researchers say these things are probably far less important than the simple act of chowing down too heartily.

The study was published in today’s issue of the New England Journal of Medicine. The researchers carefully studied 10 “diet resistant” women and men and compared them with 80 other overweight people who nonetheless believed that losing weight was possible.

Despite the small number, the researchers said they felt safe generalizing the experiment’s findings to other diet-resistant people. This was because they measured the study subjects in such minute detail and because their results were so dramatically different from the comparison group’s.

Those who claimed that they could not lose weight said they ate an average of 1,028 calories a day. In fact, they consumed 2,081. They believed that they burned up 1,022 calories a day through physical activity, but they actually exercised off only 771 calories.

The people in the comparison group were considerably more honest about their eating, although they too underestimated their calories. On average, they ate 40% more than they thought and exercised 13% less.

Heymsfield said the results mean that an underactive metabolism “is much rarer than people deluding themselves about how many calories they eat.”

However, an editorial in the journal by Drs. Elliot Danforth Jr. and Ethan A.H. Sims of the University of Vermont cautions against being too hard on overweight folks. Genes might still be to blame, perhaps by influencing their willingness to exercise or their desire to overeat.

They said the study does not prove that “obesity is simply the result of gluttony and sloth.”