Researchers at Brigham and Women's Hospital in Boston observed 21 healthy participants in a completely controlled environment for six weeks - regulating their diet, activities, hours of sleep and sleep disruptions.The study began and ended with participants sleeping an optimal 10 hours per night, but in the three weeks in between, the researchers had their subjects sleep at all different times of day and night, making sure they got just five and a half hours of shut-eye per 24-hour period.The researchers found that prolonged sleep restriction along with sleep disruption decreased the participants' resting metabolic rate and increased glucose concentrations in the blood after meals because of poor insulin secretion by the pancreas.Those effects could translate into weight gain and a risk of diabetes, and the study, published in the journal Science Translational Medicine, could shed light on how shift workers may suffer from disruptions to their "internal biological clock" or circadian rhythm."We think these results support the findings from studies showing that, in people with a pre-diabetic condition, shift workers who stay awake at night are much more likely to progress to full-on diabetes than day workers," neuroscientist and lead study author Orfeu M. Buxton said in a statement."Since night workers often have a hard time sleeping during the day, they can face both circadian disruption working at night and insufficient sleep during the day," Mr Buxton said."The evidence is clear that getting enough sleep is important for health, and that sleep should be at night for best effect."