Less sleep could mean obesity and diabetes, warn researchers with the University of South Australia (UniSA).
Dr Siobhan Banks, Research Fellow with UniSA's Centre for Sleep Research, says people who have chronically shortened sleep of just four or five hours' per night are at greater risk of being overweight and having related health problems.
"Our study results have implications for people who only get four or five hours sleep a night, which is not uncommon for some busy people during the working week," she says.
"What we have found suggests that sleep restriction may be a factor in the development of obesity and possibly type -2 diabetes as it disturbs regular, efficient metabolic functioning."
Dr Banks will present her research at 'Sleep Down Under 2010: Biodiversity of Sleep', the 22nd Annual Scientific Meeting of the Australian Sleep Association and Australasian Sleep Technologists Association being held in Christchurch, New Zealand, from October 21-23.
Ten healthy young men aged in their early 20s participated in Dr Banks' study, where they had their sleep restricted to four hours a night for five nights, to simulate a busy working week. Their diet, activity and environment were strictly controlled for a total of eight days in the lab.
At the start of the study and after the five nights' sleep restriction, they had blood sampled frequently during the day which was assayed for glucose and insulin and the fat signalling hormone leptin.
"The short term sleep restriction induced a disturbance in glucose metabolism in these otherwise healthy men, with high glucose levels that were not controlled by increases in insulin," Dr Banks says.
"There was a reduction in meal-related glucose tolerance in the morning which suggests that there must have been a rapid induction of insulin resistance. Insulin is the hormone of fat storage, so if insulin were to stay increased with chronic sleep loss, then there would be a tendency for the body to store more fat rather than breaking down energy.
"The other hormone measured, leptin, is a hormone primarily secreted by fat and it regulates energy intake and fat stores. Increasing levels of this hormone indicate that the individual has sufficient energy stored within the body. This study found that leptin increased with sleep restriction, which suggests that participants had a positive energy balance, possibly due to their sedentary behaviour in the laboratory.
"High sustained concentrations of leptin can result in leptin desensitisation so the body doesn't adequately receive the satiety feeling after eating, leading to further desire to eat."
The study was funded in part by Dr Banks' fellowship for women in science from UniSA and in part by an international collaboration with Professors Hans van Dongen and Greg Belenky at the Sleep and Performance Centre, Washington State University, Spokane.