Women cannot claim that they “get it [large butts] from their momma’s” anymore. Researchers in London found that the pressure put on areas of the body used for sitting or lying down produces up to 50 per cent more fat in those parts.

This can explain why couch potatoes and other sedentary behavior makes you fat when combined with a lack of exercise.

But even those with healthy diet and exercise habits will be affected if they spend long periods sat behind a desk.

Researchers found that preadipocyte cells – the precursors to fat cells – turn into fat cells and produce even more fat when subject to prolonged periods of ‘mechanical stretching loads’ – the kind of weight we put on our body tissues when we sit or lie down.

The researchers noted the development of liquid droplets in both the test and control groups. However, after just two weeks of stretching, the test group developed significantly more – and larger – droplets.

By the time the cells reached maturity, the group that received mechanical stretching had developed fifty per cent more fat than the control group.

Professor Amit Gefen, from Tel Aviv University, said: “Obesity is more than just an imbalance of calories. Cells themselves are also responsive to their mechanical environment. Fat cells produce more triglycerides [the major form of fat stored in the body], and at a faster rate, when exposed to static stretching.

“There are various ways that cells can sense mechanical loading. It appears that long periods of static mechanical loading and stretching, due to the weight of the body when sitting or lying, has an impact on increasing lipid [fat] production.”