Dieting is definitely not the best way to lose weight and may even pose dangers to health, a large review of previous studies by researchers at the University of California has found. Typically dieting sheds 5 to 10 percent of body weight within the first six months, but the new study found people to be heavier than their pre-dieting days just five years after they stopped dieting.

The study is published in the April issue of American Psychologist, the journal of the American Psychological Association.

UCLA researchers reviewed 31 long-term diet studies having duration of 2 to 5 years. Only a small minority of the participants were able to continue losing weight over a long period of time. A majority of dieters regained all lost weight and much more within no time, the review found.

People who went on a diet typically lost 5 to 10 per cent of their weight in the first 6 months of their dietary regimen. However 33 to 66 percent regained more weight than what they lost in the following five years.

"We found that the majority of people regained all the weight, plus more," said lead researcher Traci Mann. "Their weight would have been pretty much the same, and their bodies would not suffer the wear and tear of losing weight and gaining it all back."

Researchers say these people would have been better off not dieting in the first place. Some studies examined by the researchers appeared to rely on the participants to report their weight instead of measuring it in an unbiased manner. In other studies participants were not able to follow up resulting in mixed weight reporting.

"Diets do not lead to sustained weight loss or health benefits for the majority of people," said Dr Mann. She cited one study were all male and female participants taking part in a weight reduction programme gained a lot of weight over four years as compared to those who did go on a diet.

UCLA graduate student of psychology and co-author of the study, Janet Tomiyama said dieting indicated future weight gain on a consistent basis as showed by the reviewed studies.

A study that looked at 19,000 healthy older men over four years examined any association between lifestyle and weight gain. The conclusion? "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."

Another study had nasty surprises in store for the dieters as they weighed 11 pounds (5 kilos) more than they did at the start of the study. Dr Mann and colleagues stress that repeated weight loss and gain can increase the risk of stroke, diabetes and altered immune function.

“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," Dr Mann concluded.

The latest NHANES survey has found that obesity and overweight are rife among American adults as well as children. In order to lose weight fad diets are a popular mechanism among these groups. However as the above review points out, dieting is not all that healthy for you. A balanced diet containing plenty of fruits and vegetables combined with exercise is the optimal way to maintain health.