Exercise and dieting of little use to millions with the fat gene

MILLIONS of obese people may not be able to lose weight through diet and exercise alone, a landmark study suggests.

MORE than a fifth of obesity is genetic, a landmark study suggests.

The findings mean that millions of obese people may not be able to overcome their weight problem through diet and exercise alone.

The analysis of DNA from more than 300,000 people worldwide significantly advances the understanding of a condition that affects about a quarter of adults and a tenth of children in Britain.

It is also the most precise estimate yet for the percentage of obesity caused by DNA rather than lifestyle.

The study, carried out by the Genetic Investigation of Anthropometric Traits consortium and published yesterday (Wednesday) in Nature, could pave the way for dozens of new treatments aimed at specific causes of obesity and is expected to fuel moves to categorise obesity as a disability.

Elizabeth Speliotes, of the University of Michigan, who led the research, said it clearly showed there was no single gene that drove obesity. “The large number of genes make it less likely that one solution to beat obesity will work for all and opens the door to possible ways we could use genetic clues to help defeat obesity,” she said.

Alistair Hall, professor of medicine at the University of Leeds, who contributed data to the study, said that exercising and eating healthily were still the best protection against becoming fat, but the discovery could help many people born with a disposition to put on too much weight.”

While many people are overweight because of a combination of genes and an unhealthy lifestyle, some might owe their excess weight entirely to their DNA, Professor Hall said.

The project, a meta-analysis of 114 studies involving up to 340,000 genetic samples, tripled the number of DNA regions known to influence excess weight to almost 100. As scientists learn more about these they hope to work out why some obese people are more at risk of energy-related diseases than others.

A companion paper, also published in Nature, claimed that women are much more prone than men to genetic quirks that cause fat to accumulate around the waistline rather than the hips, exposing them to a greater risk of type-2 diabetes and cardiovascular trouble.

Out of the 20 areas of DNA linked to fat distribution that affect one sex more than the other, 19 have a stronger effect on women. The authors suggested that the disparity could be explained by sex hormones.

Karen Mohlke, professor of genetics at the University of North Carolina and one of the paper’s senior authors, said the discoveries would help scientists to establish which genes made people most vulnerable to conditions including heart disease and diabetes.

The findings came as experts warned that obesity is a “chronic disease” that cannot be cured by simply eating less and moving more. While many obese people can lose weight for a few months, the vast majority will put it back on, doctors warned, and should only be considered to have “obesity in remission”.

Writing in The Lancet Diabetes & Endocrinology, the experts said the condition’s causes were largely biological.

The Times