Obesity: When nature gets the better of nurture

New research adds weight to the argument that some people can gain weight despite healthy eating and exercise habits. Tapping data from nearly a quarter-million people and more than 40 studies, an international consortium has identified 18 new gene sites associated with obesity and 13 that affect how fat is distributed on the body. It’s a significant advance, adding to just 14 previously known gene sites linked to body mass index (BMI) and just one linked to waist-to-hip ratio.

As with a recent study of height, conducted by the same “GIANT” consortium, the analyses also showed an additive effect: people who carried more than 38 variants linked to an increased BMI averaged 15 to 20 pounds heavier than those who carried fewer than 22 such variants.

So why is obesity on the rise? While we swim in roughly the same obesity gene pool as our ancestors, the waters have become more polluted and stagnant — we’re awash in high-calorie foods and getting less exercise than ever. Some of these effects appear to occur before birth.

The solution could come from further studying the leaner folks, who manage to stay trim without particular attention to diet or exercise. “If we could understand a lot more about why people are resistant to our environment and stay lean despite all the pressures there are to gain weight, we’d have a better shot at getting better therapies than we have now,” Joel Hirschhorn, a Children’s researcher involved in the analyses, tells the Wall Street Journal.