Diet and exercise may not be enough

While doctors may prescribe diet and exercise as a remedy for obesity, a new study shows that regaining weight may be inevitable due to forces outside people's control: hormones.

After tracking 50 overweight or obese adults on a low-calorie diet over a 10-week period, Australian researchers found that once participants lost weight, hormone levels -- particularly those that influence hunger -- shifted in the body, leading to increase appetites and weight regain.

The study involved 50 adults with a body mass index (BMI) or between 27 and 40, averaging 95 kg (209 lbs). After an initial loss of about 13 kg (29 lbs) scientists at the University of Melbourne found that the levels of appetite-regulating hormones changed, resulting in a regain of about 5 kg (11 lbs) over the course of a year.

The new findings, published in The New England Journal of Medicine last week, throws a wrench in the conventional message that diet and exercise alone are enough to maintain a healthy weight and reveals the important role hormones play in regulating body weight, pointed study co-author Joseph Proietto.

"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," he said in a statement.

Worldwide, more than 1.5 billion adults are considered overweight, and 400 million are obese. In Australia, it's estimated that 50 percent of women and 60 percent of men are either overweight or obese.

To pre-empt the onset of obesity, Proietto suggests it would be more effective to start young and focus public health efforts towards children.

"The study also suggests 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 said

The results of the Australian study corroborate findings in another paper released earlier this year, in which researchers from Spain confirmed that people with high levels of the hormone leptin and low levels of ghrelin are more likely to gain the weight they lost.

Instead of playing the diet and exercise message on repeat -- an ineffective longterm weight loss strategy for some -- the Spanish authors suggested that endocrinologists and nutritionists consider the possibility of hormonal imbalances when developing weight loss strategies.

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