No matter how much weight you loose dieting, it will always come back, warn researchers. And, to make matters worse for people who keep going on diets to get rid of those extra pounds, the researchers also warn that when the weight comes back, it’s highly likely that you will be a few kilos heavier that you were before you went on the diet.
The study was conducted by researchers at the University of California, Los Angeles, led by Traci Mann, UCLA associate professor of psychology. Mann insisted that though dieting could see a persons weight drop by 5 to 10 percent, the loss was not sustainable in most cases.
"You can initially lose 5 to 10 per cent of your weight on any number of diets, but then the weight comes back. We found that the majority of people regained all the weight, plus more," she said.
"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 added.
The researchers, whose findings are based on an analysis of 31 long-term diet studies, found that while people on diets typically lose 5 to 10 percent of their starting weight in the first six months, at least one-third to two-thirds of people on diets regain more weight than they lost within four or five years, and the true number may well be significantly higher.
"Although the findings reported give a bleak picture of the effectiveness of diets, there are reasons why the actual effectiveness of diets is even worse," Mann said.
The researchers also noted 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.
"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, 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.
So if dieting doesn't work, then the question becomes - what does? The answer is eating in moderation and getting regular exercise.
"Eating in moderation is a good idea for everybody, and so is regular exercise. That is not what we looked at in this study. Exercise may well be the key factor leading to sustained weight loss. Studies consistently find that people who reported the most exercise also had the most weight loss," Mann said.
Evidence suggests that repeatedly losing and gaining weight is linked to cardiovascular disease, stroke, diabetes and altered immune function.
The researchers now recommend that more research be conducted on the health effects of losing and gaining weight, noting that scientists do not fully understand how such weight cycling leads to adverse health effects.