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"The idea was not just to look at run-of-the-mill obesity, but look for genetic factors that may affect people who have more severe problems with their weight," said Dr. Sladek, an assistant professor in the Department of Human Genetics and Endocrinology. "This includes children who become obese at a young age, before the age of six. We also studied the genomes of adults who had a familial history of severe obesity, with a body-mass index greater than 40." People are generally defined as "overweight" if they have a body-mass index greater than 25.

"The family approach being undertaken by our collaboration with our colleagues in France is going to become important for future large-scale genetic studies," Sladek continued. "Our suspicion is that a lot of the genetic changes that make people obese will turn out to be variants that run in families or in segments of the population, rather than things that are very common across the population. In terms of diabetes, we think that perhaps 90 per cent of the genetic risk could come from these familial or even personal genetic variants."