The study found that otherwise-healthy adults who were both sleep deprived and sleeping on schedules that put them at odds with their biological clocks -- common problems for millions of people who work at night -- made 32% less insulin, the hormone that controls blood sugar, than they do when they are well rested.
As a result, their blood sugar rose significantly. In some cases, those increases reached pre-diabetic levels.
The number of calories they burned at rest also dropped about 8%. Over the course of a year, researchers think that could translate into a weight gain of nearly 13 pounds.
"What that means is that the modern condition of excess work, excess pressure, no sleep -- all this disruption -- we can't adapt well to it metabolically. This is a maladaptive response to modern life," says researcher Orfeu M. Buxton, PhD, an associate neuroscientist in the division of sleep medicine at Brigham and Women's Hospital in Boston.
Measuring the Impact of Poor Sleep
For the study, published in the journal Science Translational Medicine, researchers had 21 men and women live in carefully controlled conditions in a sleep lab for more than a month.
About half the adults in the study were in their 20s, the other half were in their 60s. All were healthy and well rested at the start of the study.
They lived in dimly lit rooms without windows, which prevented their bodies from adjusting to shifting days and nights.
For three weeks, researchers kept people in the study awake for 28 hours at a stretch. That meant they were sometimes eating in the middle of their biological nights and sleeping during their biological days. They were allowed to sleep for less than six hours in each 24-hour period, conditions meant to create sleep deprivation.
Researchers used blood tests to measure blood sugar before and after meals, and to measure hormones related to stress, energy regulation, and appetite.
During the periods of sleep deprivation and disruption, people burned fewer calories at rest than they did when they'd had adequate sleep. They also had higher blood sugar. That was true regardless of their age or sex.