Diets don't work?
<url>Will you lose weight on a diet, and, most importantly, will you keep the resulting weight?
Probably not, UCLA (University of California, Los Angeles) researchers say in the April issue of American Psychologist, the journal of the American Psychological Association.
"You can initially lose 5-10 percent of your weight on any diet, but then the weight comes back," says Tracey Mann, associate professor of psychology at UCLA and lead author of the study. "We found out that most people return all the lost kilograms and gain more. According to the results of the study, only a small number of participants manage to maintain the lost weight, while the majority gain weight completely. Diets do not lead to sustained weight loss or improved health in most people."
Mann and her co-authors conducted a comprehensive and thorough analysis of diet studies, analyzing 31 long-term studies.
"What happens to dieters in the long term? Mann asks. – Wouldn't it be better not to go on a diet at all? We decided to find and analyze every study where we observed people who followed a diet for two to five years. We concluded that it would be better for most of them not to go on a diet at all. Their weight would be almost the same, and the body would not suffer from wear and tear as a result of weight loss and subsequent weight gain."
Dieters usually lose 5-10 percent of their original weight in the first six months, the researchers found. However, according to the results of studies analyzed by them, from one-third to two-thirds of people after dieting gain more weight than they lost within four to five years. And in reality, the picture can be even scarier.
"Although the results of the study paint a disappointing picture regarding the effectiveness of diets, there are reasons to suspect that in reality the situation is even worse," says Mann.
Mann argues that certain factors distort research results so that diets seem more effective than they actually are. For example, many participants themselves indicate their weight by phone or by mail, although their weight should be measured and registered by a disinterested person. In addition, the proportion of patients who remained under observation was very low – in eight studies, this figure was below 50 percent. And those participants who responded are probably not typical representatives of the whole group, because, according to Mann, people who have gained a lot of pounds are usually reluctant to show up for the necessary check.
"Several studies have indicated that dieting is actually a reliable indicator of weight gain in the future," says Janet Tomiyama, a graduate student in the UCLA Department of Psychology and co–author of the study. "One study found that both men and women who participated in official weight loss programs gained significantly more kilograms over a two–year period than those who did not participate in weight loss programs," she claims.
Another study, which examined various lifestyle factors and their relationship to weight changes in more than 19,000 healthy older men, revealed that one of the most reliable indicators of weight gain over four years is weight loss on a diet at some point years before the study. "In several studies, people from the control groups who did not follow a diet felt no worse, and in some cases better, than those who were on a diet," says Tomiyama.
If diets don't work, then what will help?
"A moderate diet is a good way to control weight, as well as regular exercise," says Mann. – But that's not what we studied in our study. Exercise can be a key factor leading to sustained weight loss. Studies constantly show that people who have been exercising the most also lose weight more than others."
Mann says that studies of diets lasting less than two years are too short to demonstrate whether people are gaining lost weight again.
"Even when you've been watching people for four years, they still continue to gain weight," she claims.
In one study, dieters suffering from obesity were observed for different periods of time. Among those who were followed for less than two years, 23 percent gained more weight than they lost, while of those who were followed for at least two years, 83 percent gained more weight than they lost. One study found that the weight of 50 percent of dieters exceeded the initial weight by more than 10 kg five years after the end of the diet, Mann tells us.
There is evidence that cyclic weight loss-weight gain is associated with cardiovascular diseases, strokes, diabetes and changes in the immune system. Mann and Tomiyama recommend conducting additional research on the impact of weight loss-weight gain on health, noting that scientists do not fully understand how such weight jumps lead to adverse health consequences.
Mann notes that her mother tried various diets and was unable to maintain weight after them. "My mom was on a diet and claims that our conclusions are obvious," she says.
Although the researchers analyzed 31 dieting papers, they did not evaluate individual diets.
Medicare raised the question of whether obesity is a disease by removing the words "Obesity is not considered a disease" from its documentation in 2004. "This allows Medicare to consider allocating funds for the treatment of obesity," Mann notes.
"Diets are ineffective in treating obesity,– says Mann. – We recommend that Medicare does not fund weight loss programs with a diet as a remedy for obesity. The benefits of dieting are too small and the potential harm is too great to recommend a diet as a safe effective treatment for obesity."
"From 1980 to 2000, the percentage of Americans who are obese more than doubled, rising from 15 to 31 percent of the population," Mann notes.
Mann, a social psychologist, taught a nutrition psychology seminar for UCLA applicants four years ago. After completing the course, she and her students continued their research. Mann's co-authors are Erica Westling, Anne-Marie Liu, Barbra Samuels and Jason Chatman.
"We wondered what the evidence is that diets are effective in the long run, and found that the evidence demonstrates the opposite," says Tomiyama.
In his future research, Mann will try to find out whether a combination of diet and exercise is more effective than exercising on its own.
Portal "Eternal youth" www.vechnayamolodost.ru
09.04.2008