The ill effects of getting too little sleep — weight gain and increased diabetes risk among them — have been known for a long time, but now researchers think they’ve identified the cellular process for how sleep deprivation takes its toll. Just a few nights of scant sleep reduces the response of fat cells to the hormone insulin, which puts the body, at least temporarily, into a state akin to pre-diabetes.

A small clinical trial published last Monday in the Annals of Internal Medicine compared fat cells in seven college students both before and after they slept 4.5 hours a night for four consecutive nights and found that their cells were 30 percent less responsive to insulin after their period of sleep deprivation.