New research suggests that people's genes are key to helping them stay slim. A study from Cambridge University in the U.K. discovered that thin people had DNA that contained variants which helped them stay slim and fewer variants linked to being overweight. Researcher Sadaf Farooqi, professor of metabolism and medicine, said: "We've found that there are genes associated with thinness." She added: "Genes play at least 40 per cent of a role in people's weight. It's much more than people realize." This might help explain why some people are naturally skinny while others have big problems with keeping their weight down and seem to pile on the pounds so easily.

The study is published in the journal PLOS Genetics. The researchers said they undertook the study to find out why so many people struggle with their weight. Over 30 per cent of American adults are obese, while a staggering 94.5 per cent of adults on the South Pacific island of Nauru are overweight. Professor Farooqi said she wanted to help people who are struggling with their weight. She said: "It's easy to rush to judgment and criticize people for their weight, but the science shows that things are far more complex." She added: "Healthy, thin people are generally thin because they have a lower burden of genes that increase a person's chances of being overweight and not because they are morally superior."