Scientists have found a gene that could explain obesity.

They say it gives the people carrying it a bigger appetite and makes them more likely to overeat.

The discovery is the best evidence yet that some people are predisposed to a fuller figure, while others find it easier to stay slim.

The GAD2 gene speeds up production of a chemical that boosts the appetite and drives the stimulus to eat too much, according to the study by Imperial College, London.

DNA scans of more than 1,200 people showed that carriers were ‘significantly more likely’ to give in to hunger.

Lead researcher Professor Philippe Froguel said: ‘The discovery that this one gene plays a role in determining whether someone is likely to overeat could be crucial in understanding the continued rise in obesity rates around the world.

‘Genetic factors alone can not explain the rapid rise in obesity rates, but they may provide clues to preventative and therapeutic approaches that will ease the health burden associated with obesity.’

Treatments to ‘switch off ’ or slow down GAD2 would be a huge step in stemming the obesity epidemic threatening the Western world.

Obesity rates in England have trebled in the past 25 years and treatment and related care now cost the Health Service £2.5billion a year.

Research shows that being seriously overweight takes an average of ten years off a normal lifespan because it increases the risk of cancer, diabetes, heart attacks and strokes. Obesity is blamed for 30,000 deaths a year in Britain.

The Imperial College study revealed that GAD2 speeds up production of a chemical messenger in the brain called GABA, or gamma-amino butyric acid. When combined with another molecule, GABA stimulates us to eat.