Study finds that dieters who have regained weight have to fight persistent biological urge
By NEW YORK TIMES, ASSOCIATED PRESS, BLOOMBERG
NEW YORK: Any dieter knows that it is hard to keep off weight you have 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.
In the study, by Australian researchers, healthy people who were either overweight or obese were put on a highly restricted diet that led them to lose at least 10 per cent of their body weight. They then kept them on a diet to maintain that weight loss.
A year later, the researchers found that the participants’ metabolism and hormone levels had not returned to the levels before the study started.
The study, published yesterday in The New England Journal of Medicine, is small and far from perfect, but confirms their convictions about why it is so hard to lose weight and keep it off, say obesity researchers who were not involved in the study.
They cautioned that the study did not include a control group, for purposes of comparison. Moreover, the study had only 50 subjects, and 16 of them quit or did not lose the required 10 per cent of their body weight.
And while the hormones studied have a logical connection with weight gain, the researchers did not show that the hormones were causing the subjects to gain back their weight.
Nonetheless, Dr Rudolph Leibel, an obesity researcher at Columbia University, said while it came as no surprise that hormone levels changed shortly after the participants lost weight, ‘what is impressive is that these changes don’t go away’.
Dr Stephen Bloom, an obesity researcher at Hammersmith Hospital in London, said the study needed to be repeated under more rigorous conditions, but added: ‘It is showing something I believe in deeply – it is very hard to lose weight.’ And the reason, he said, is that ‘your hormones work against you’.
In the study, Mr Joseph Proietto and his colleagues at the University of Melbourne recruited people who weighed an average of 95kg.
At the start of the study, his team measured the participants’ hormone levels and assessed their hunger and appetites after they ate a boiled egg, toast, margarine, orange juice and crackers for breakfast.
The dieters then spent 10 weeks on a very low calorie regimen of 500 to 550 calories a day designed to make them lose 10 per cent of their body weight.
In fact, their weight loss averaged 14 per cent, or 13kg.
As expected, their hormone levels changed in a way that increased their appetites, and indeed they were hungrier than when they started the study.
They were then given diets designed to maintain their weight loss. A year after they had lost the weight, the researchers repeated their measurements.
The subjects were gaining the weight back despite the maintenance diet – they had gained back on average half of what they had lost – and the hormone levels offered a possible explanation.
In normal times, leptin, a hormone produced by fat cells, sends signals to brain receptors to reduce food intake once a person is full, and boost metabolism.
During the 10 weeks of the study’s diet, leptin levels plunged 65 per cent. They remained 35 per cent below their original levels a year later.
The amount of ghrelin, which stimulates hunger, rose significantly with weight loss and remained higher at the end of the study.
The end result was that volunteers reported a significant increase in appetite while losing weight, and said they still felt hungry a year later, the researchers found.
Similar fluctuations were recorded with half a dozen other compounds believed to regulate appetite.
So until researchers understand the hormone swings better, one should for now stick with the tried and true to lose weight.
‘Until we know more, we should continue to promote the things we know – sustainable lifestyle choices, physical activity and a healthy diet. We are not ready to turn that upside down yet,’ said Dr Donald Hensrud, the chairman of preventive medicine at the Mayo Clinic in Rochester, Minnesota, who was not involved in the study.
A LOSING BATTLE
‘It is showing something I believe in deeply – it is very hard to lose weight… your hormones work against you.’
Dr Stephen Bloom, an obesity researcher at Hammersmith Hospital in London