The less you sleep, the more likely you are to gain weight, and a new study suggests why: late night nibbling translates into too many excess calories. The study, from the University of Pennsylvania, showed that participants in a laboratory sleep study whose shut-eye was limited to four hours per night for five nights, bumped up their daily intake of calories during the wee hours until their four a.m. bedtime. The researchers also reported that the proportion of calories from fat consumed by the night owls was higher late at night than earlier in the day.
The other study participants were allowed a lot more sleep – from 10 p.m. until 8 a.m. A total of 225, healthy, non-obese adults age 22 to 50 participated in the study. Among those randomly selected to sleep only four hours per night, men gained more weight than women, and African-Americans gained more than Caucasians. During the study, meals were served at scheduled times, but participants had around-the-clock access to food in the lab kitchen. No exercise was permitted.
