Your 2 am bedtime is probably making you fat

Sleep duration of at least 6.5 hours is associated with higher fast food consumption and lower vegetable intake

If your favourite novels are stealing that precious sleep time from you, don't be surprised if you have to start squeezing into your skinny jeans.

A new study from the Northwestern University suggests that among healthy adults with habitual sleep duration of at least 6.5 hours, late sleep timing was associated with higher fast food consumption and lower vegetable intake, particularly among men, as well as lower physical activity.

Results show that late sleep timing is associated with lower body mass index and is not associated with total caloric intake; however, it remains associated with poorer diet quality, particularly fast food, vegetable and dairy intake.

"Our results help us further understand how sleep timing in addition to duration may affect obesity risk," said principal investigator Kelly Glazer Baron, adding "It is possible that poor dietary behaviors may predispose individuals with late sleep to increased risk of weight gain."

The study group consisted of 96 healthy adults between the ages of 18 and 50 years with sleep duration of 6.5 hours or more. The study involved 7 days of wrist actigraphy to measure sleep, food diaries to measure caloric intake and dietary patterns, and SenseWear arm band monitoring to measure physical activity. Dim light melatonin onset was evaluated in the clinical research unit. Body fat was evaluated using dual axis absorptiometry (DXA). Data were analyzed using correlation and regression analyses controlling for age, sex, sleep duration and sleep efficiency.

The research appears in the journal Sleep.