Lose weight. Regain it. Blame hormones?

U. MELBOURNE (AUS) — Obese people may regain weight after dieting due to hormonal changes, a new study shows.

Worldwide, there are more than 1.5 billion overweight adults, including 400 million who are obese. In Australia, it is estimated more than 50 percent of women and 60 percent of men are either overweight or obese.

Although restriction of diet often results in initial weight loss, more than 80 percent of obese dieters fail to maintain their reduced weight.

Published in the New England Journal of Medicine, the study involved 50 overweight or obese adults, with a BMI of between 27 and 40, and an average weight of 95 kg (209 pounds), who enrolled in a 10-week weight loss program using a very low energy diet.  A kilogram is equal to 2.2 pounds.

Levels of appetite-regulating hormones were measured at baseline, at the end of the program, and one year after initial weight loss.

The results showed that following an initial weight loss of about 13 kgs, the levels of hormones that influence hunger changed in a way that would be expected to increase appetite. These changes were sustained for at least one year. Participants regained around 5kgs during the one-year period of study.

The study shows the important roles that hormones play in regulating body weight, making dietary and behavioral change less likely to work in the long-term, says Joseph Proietto, professor from the University of Melbourne and Austin Health.

“Our study has provided clues as to why obese people who have lost weight often relapse. The relapse has a strong physiological basis and is not simply the result of the voluntary resumption of old habits.”

Although health promotion campaigns recommended obese people adopt lifestyle changes such as being more active, they are unlikely to lead to reversal of the obesity epidemic.

“Ultimately it would be more effective to focus public health efforts in preventing children from becoming obese. The study also suggested that hunger following weight loss needs to be addressed. This may be possible with long-term pharmacotherapy or hormone manipulation but these options need to be investigated,” he says.

The study was done in collaboration with La Trobe University.

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