Sleepless nights may cost you more than sweet dreams. The latest research has found that a lack of sleep may cause weight gain, not to mention a variety of other health problems like high blood pressure, stroke and diabetes. A study was conducted where 7 subjects had 4 straight nights of 8.5 hours of sleep and then one month later had 4 straight nights of 4.5 hours sleep. Researchers found that the participants’ fat cells were less sensitive to insulin after a restricted night of sleep. Insensitivity to insulin, which controls blood sugar, has been linked to a host of health problems including diabetes and obesity. While scientists have already suspected that lack of sleep can cause weight gain it was assumed that you were just likely to eat more and get less activity when you were sleep deprived. This is the first study to link lack of sleep to a change in fat cell function. While most people think that they can function on 4 or 5 hours of sleep it seems that 8 hours is still the magic number for metabolic function.