You know that not enough shut-eye makes you irritable, but did you know that lack of sleep has also been linked to diabetes and weight gain? Researchers had not understood why, although one theory links it to a rise in the stress hormones, cortisol.
Some recent research, recently reported in New Scientist 20 October 2012, from the University of Chicago suggests another answer (Annals of Internal Medicine, DOI:10.7326/0003-4819-157-8-201210160-00005).
Matthew Brady and his team tested fat cells taken from the bellies of seven adults who slept for 4 nights for up to 8 and a half hours and then another 4 nights for only 4 and half hours.The team found that after sleep deprivation fat cells were 30 percent less responsive to insulin (a hormone that makes muscle, liver and fat cells take up glucose after a meal). This leads to higher blood glucose levels which are linked to diabetes. Fat cells also release the appetite regulating hormone leptin, and this mechanism may also be disrupted by lack of sleep.
The researchers were surprised by the strength of the response to lack of sleep. As they pointed out, four nights of sleep curtailment "represents a real world situation, such as sitting for final exams or having a newborn in the house".