It may not seem like rocket science, but researchers have discovered that sitting around really does make your backside bigger.
According to the research by Tel Aviv University, couch potatoes that sit around for long periods of time put pressure on the preadipocyte cells, causing the body to produce 50% more fat than usual.
In a bid to explain why sedentary behaviour causes weight-gain, scientists believe that the precursors to fat cells turn into flab (and end up producing more) when subjected to prolonged periods of sitting down, otherwise known as "mechanical stretching loads".
The study involved looking at MRI images of the muscle tissue of patients paralysed by spinal cord injuries. Researchers noticed that over time lines of fat cells were invading and outnumbering major muscles in the body.
Researchers found that when extended amounts of force is put upon a particular area in the body, fat tissue is encouraged to expand.
To investigate this further, scientists placed individual cells in a cell-stretching device, attaching them to a flexible, elastic substrate.
The cells were stretched consistently, mimicking long periods of sitting down while other cells were left alone. Researchers found that after two weeks of stretching, the cells developed a significantly larger amount of fatty liquid droplets than those that weren't stretched.
By the time cells reached maturity, the stretched cells had 50% more fat than the normal cells.
"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," says Professor Anit Grefen from the study.
"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."
The study, published in the American Journal of Physiology, warned that even those who took regular exercise were at risk of gaining weight if they spent a long period of time sitting down.