Dieters struggle against powerful hormonal urge, research finds

ANY dieter knows that it’s hard to keep off weight you’ve lost. Now a study finds that even a year after dieters shed a good chunk of weight quickly, their hormones were still insisting, “Eat! Eat! Eat!”

The findings suggest that dieters who have regained weight are not just slipping back into old habits, but are struggling against a persistent biological urge.

“People who regain weight should not be harsh on themselves, as eating is our most basic instinct,” Joseph Proietto of the University of Melbourne in Australia, an author of the study, said.

Weight regain is a common dieting problem. To study what drives it, Proietto and his colleagues enrolled 50 overweight or obese patients in a 10-week diet programme in Australia. They wanted to see what would happen in people who lost at least 10% of their body weight. Ultimately, only 34 people lost that much and stuck with the study long enough for analysis.

On average, participants lost almost 30 pounds during the 10 weeks, faster than the standard advice of losing 1 or 2 pounds a week. They took in 500 to 550 calories a day, using a meal replacement called Optifast plus vegetables, for eight weeks. Then for two weeks they were gradually reintroduced to ordinary foods.

Despite counselling and written advice about how to maintain their new weights, they gained an average of 12 pounds back over the next year. So they were still at lower weights than when they started.

The scientists checked the blood levels of nine hormones that influence appetite. The key finding came from comparing hormone levels from before the programme to one year after it was over. Six hormones were still out of whack, boosting hunger.

The dieters said they felt hungrier after meals at the one-year mark, compared to what they felt before the programme began.

Experts said that the persistent effect on hormone levels was not surprising, and it probably had nothing to do with the speed of the weight loss.

People who lose less than 10% of body weight would probably show the same thing, to a lesser degree, said Dr George Bray of the Pennington Biomedical Research Centre in Louisiana.

A key message of the study is that “it’s better not to gain weight than to try to lose it,” Dr Bray said.

The study appears in the New England Journal of Medicine.