Couch potatoes could soon be popping a pill to cure them of their laziness after Scottish scientists found the behavioural habit may be down to their genes.

Experts at Aberdeen University, working with other researchers in a joint project in China, compared normal mice with those that had a mutation in a gene called SLC35D3.

They found that the mutation affected dopamine feel-good signals in the brain, which in turn affected the regulation of their physical activity levels.

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The Chinese mice walked about one-third less than normal mice, became fat, and developed other ­symptoms ­similar to a condition in people called metabolic syndrome - a medical term for a combination of diabetes, high blood pressure and obesity.

However, when the affected mice were treated with a drug that activates dopamine receptors, they became more active and lost weight. It raises the ­prospect of pills tailored to couch ­potatoes to cure them.

Professor John Speakman, who is involved in the research, said: "There are a large number of people worldwide that have metabolic syndrome."