A rising number of overweight people may also be to blame for global warming according to the London School of Hygiene and Tropical Medicine.

The study says obese people are responsible for emitting at least a ton more of climate-warming carbon dioxide per year than thin people.

"Moving about in a heavy body is like driving in a gas guzzler," Dr. Phil Edwards, of the London School of Hygiene and Tropical Medicine, said.

Researchers say the extra food needed for fat people adds to carbon emmissions that heat up the world, melting polar ice caps, raising sea levels and killing rain forests.

Fat people are also more likely to travel by car which increases carbon emmissions.