Yet another reason to avoid the couch potato lifestyle - scientists have found that such inactivity actually creates fat within fat cells, making excess weight even harder to shift.
A study from Tel Aviv University found preadipocyte cells - the precursors to fat cells - turn into fat cells faster 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.
So by slumping in front of the TV this Christmas, you are not only burning less calories, you are actually encouraging fat cell production!
Professor Amit Gefen of TAU's Department of Biomedical Engineering said: "Obesity is more than just an imbalance of calories. Cells themselves are also responsive to their mechanical environment. Fat cells produce more triglycerides, and at a faster rate, when exposed to static stretching."
Next, the research team plan to look at how long a period of time a person can sit or lie down without the mechanical load becoming a factor in fat production. But in the meantime, it certainly can't hurt to get up and take an occasional stroll!