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Canadian scientists prove link between the gene that causes obesity and rates of depression

The old saying 'fat people are more jolly' has more than a grain of truth to it. It turns out there's good reason for the stereotypical "happy" fat person immortalised in characters like Santa Claus - it's genetic.

Scientists from McMaster University in Canada have found that the so-called 'fat gene' FTO is also responsible for people's sense of wellbeing or happiness.

FTO is a genetic contributor to obesity but it also reduces the risk of depression by up to eight per cent.

The scientists studied 17, 200 DNA samples in a study investigating the psychiatric health of a group of people from over 21 nations. The finding that FTO lead to a lower rate of depression was backed up by three further international studies.

While eight per cent might not sound significant, Professor David Meyre, of McMaster University in Canada, said that it was the "first evidence that an FTO obesity gene is associated with protection against major depression, independent of its effect on body mass index."

He said the discovery won't change the day-to-day treatment of patients, it identifies a "a novel molecular basis for depression."