Dieting is not as effective as many people think
By BARRY GLASSNER
LOS ANGELES TIMES
'Tis the season to diet. In an annual ritual that mostly benefits the 30 billion weight-loss industry, Americans by the multimillions will atone for gorging over the holidays by depriving themselves over the coming weeks.
With nearly two-thirds of us officially overweight or obese, according to the Centers for Disease Control and Prevention, it may seem odd, if not downright unpatriotic, to suggest that we reconsider dieting. But the fact is, there's little evidence for the wisdom of mass dieting.
On the contrary, as researchers from Harvard and Stanford observed in a 2003 paper, for substantial numbers of people, "dieting to control weight is not only ineffective, it may actually promote weight gain."
The scientists made that assertion in the journal Pediatrics, in which they reported the results of a study of almost 15,000 boys and girls ages 9 to 17. Over the three years that researchers followed them, dieters in the sample gained more weight than the non-dieters and were more likely to engage in binge eating.
Another set of studies by a group of psychologists and nutritionists found that young girls are more likely to become overweight or obese later in life if their parents put them on diets. Still another study, conducted by the University of California, Berkeley, found that the heaviest adults were those who had begun dieting at a younger age and had done so more often than the rest.
In part, these studies may reflect the fact that the people most likely to diet early and often are those who already have a tendency to be heavy. But if dieting were an effective route to long-term weight loss, wouldn't we expect them to get thin and stay thin?
The reality is otherwise. Just about any diet scheme will result in temporary weight loss for almost anyone who follows it rigorously. Review the scientific evidence, though, and you discover that only a small proportion of people succeed in taking off much weight and keeping it off, even with the best of care.
Consider a 2002 study in the New England Journal of Medicine conducted by physicians from obesity programs within the National Institutes of Health. People who devotedly diet, exercise and get counseling for four to six weeks can expect to lose 5 percent to 10 percent of their weight, the researchers auspiciously report. Then, echoing the conclusions of numerous other studies, they add: "For the vast majority of persons, weight loss is followed by a slow, inexorable climb to the pre-intervention body weight -- or even higher."
Temporary reductions might be valuable in their own right were yo-yo dieting not associated with adverse effects on the dieters' immune and circulatory systems, ego and offspring.
Rather than go on a New Year's diet, we would do better to resolve to eat well and moderately throughout the year.
Glassner, professor of sociology at the University of Southern California, is author of the newly published "The Gospel of Food."