All Diets Fail To Keep Off Weight

UCLA researchers confirm what you already know: diets do not work for sustained weight loss.

Will you lose weight and keep it off if you diet? No, probably not, UCLA researchers report in the April issue of American Psychologist, the journal of the American Psychological Association. "You can initially lose 5 to 10 percent of your weight on any number of diets, but then the weight comes back," said Traci Mann, UCLA associate professor of psychology and lead author of the study. "We found that the majority of people regained all the weight, plus more. Sustained weight loss was found only in a small minority of participants, while complete weight regain was found in the majority. Diets do not lead to sustained weight loss or health benefits for the majority of people." Mann and her co-authors conducted the most comprehensive and rigorous analysis of diet studies, analyzing 31 long-term studies.

The researchers analyzed all studies that followed dieters from 2 to 5 years. None of them worked. Worse, these studies contain biases that overstate the benefits of the diets.

Mann said that certain factors biased the diet studies to make them appear more effective than they really were. For one, many participants self-reported their weight by phone or mail rather than having their weight measured on a scale by an impartial source. Also, the studies have very low follow-up rates  eight of the studies had follow-up rates lower than 50 percent, and those who responded may not have been representative of the entire group, since people who gain back large amounts of weight are generally unlikely to show up for follow-up tests, Mann said.

Dieting is even worse than not dieting.

"Several studies indicate that dieting is actually a consistent predictor of future weight gain," said Janet Tomiyama, a UCLA graduate student of psychology and co-author of the study. One study found that both men and women who participated in formal weight-loss programs gained significantly more weight over a two-year period than those who had not participated in a weight-loss program, she said. Another study, which examined a variety of lifestyle factors and their relationship to changes in weight in more than 19,000 healthy older men over a four-year period, found that "one of the best predictors of weight gain over the four years was having lost weight on a diet at some point during the years before the study started," Tomiyama said. In several studies, people in control groups who did not diet were not that much worse off  and in many cases were better off  than those who did diet, she said.

In a way this is great news for anyone who doesn't want to diet. You don't need to feel guilty about it. If you diet you'll just gain more weight in the long run. My guess is the body treats the scarcity of food while on a diet as a sign that it needs to build up fat stores in case another lean period happens.

So how to lose weight? The Mann and Tomiyama suspect that exercise will best keep people skinny. But their latest analysis was restricted to the effects of dieting.

People faced with morbid obesity can do the stomach surgey that restricts stomach size. That appears to work pretty reliably. Also, get enough sleep. Lack of sleep has been found a contributor to weight gain in other studies. Also, at least eat healthy foods regardless of how much food you eat.

I'd like to see more studies on the effect of eating various ratios of different types of fats and sugars. Does fructose consumption contribute to obesity? Do some fats sate hunger for longer than other fats? Do low glycemic index foods sate hunger for longer? In addition to how much we eat, what we eat might matter for weight control.