Do you want to chill out and relax by stretching out on the couch? Do this only if you want to get fat — lounging on the couch is an "active inactivity" and can cause you to gain weight, says Professor Amit Gefen of Tel Aviv University.
This type of inactivity encourages the body to create new fat in fat cells, says Gefen. His research, published in the American Journal of Physiology — Cell Physiology, found that lying on a couch causes preadipocyte cells — the precursors to fat cells — to turn into fat cells more quickly and to produce even more fat when they are subjected to periods of "mechanical stretching loads" — the kind of weight put on body tissues when we sit or lie down.
"Obesity is more than just an imbalance of calories," Gefen says. "Cells themselves are also responsive to their mechanical environment. Fat cells produce more triglycerides, and at a faster rate, when exposed to static stretching."
Gefen's work with bedridden and wheelchair-bound patients who had chronic wounds sparked his research. He found that, over time, MRI imaging showed fat cells invaded major muscles. That observation sparked an investigation into how mechanical load — the amount of force placed on a specific area — could encourage fat tissue to spread.
In his study, he stimulated preadipocytes with glucose or insulin to change them into fat cells. Then individual cells were put in a cell-stretching device and were stretch for long periods of time, simulating sitting or lying down for prolonged periods. After only two weeks of stretching, the cells were larger. By the time they reached maturity, the stretched cells had developed 50 percent more fat than the control cells that hadn't been stretched.
Gefen believes his study shows that people should take more than just calories into account. Too sedentary a lifestyle, such as spending most of their day sitting at a desk, can increase fat even though they eat a healthy diet and exercise.
Next, Gefen will investigate how long a person can sit or lie down without the mechanical load influencing fat production. In the meantime, he suggests, it can't hurt to stand and take an occasional stroll.
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