Sitting around really does give you a big backside, scientists have revealed.
Researchers 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 preadolescence 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.
By studying MRI images of the muscle tissue of patients paralyzed by spinal cord injuries, they noticed that, over time, lines of fat cells were invading major muscles in the body.
This spurred an investigation into how mechanical load – the amount of force placed on a particular area occupied by cells – could be encouraging fat tissue to expand.
A team stimulated preadipocytes with glucose or insulin to turn them into fat cells. They then placed individual cells in a cell-stretching device, attaching them to a flexible, elastic substrate – or underlying.
The test group of cells were stretched consistently for long periods of time, representing extended periods of sitting or lying down, while a control group of cells was not.
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.
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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.”
These findings indicate that we need to take our cells’ mechanical environment into account as well as pay attention to calories consumed and burned, said Professor Gefen.
He warned that, while there are extreme cases of people confined to wheelchairs or beds due to medical conditions, many people live a too sedentary lifestyle – spending most of the day behind a desk.
Even somebody with a healthy diet and exercise habits will be negatively impacted by long periods of inactivity.
The research has been published in the American Journal of Physiology – Cell Physiology.