Sleeping less than 7 hours a night may mean that people are eating and drinking more, contributing to obesity, says research published in the American Journal of Health Promotion.

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People who lack sleep are also more likely to eat while doing activities like watching TV.

The association between short sleep and obesity is already known, but the present study focuses on a new aspect of the association between sleep and obesity: whether short sleep is linked to more time spent in secondary eating or drinking.

“Secondary eating and drinking” refers to eating or drinking beverages other than water, such as sugar-sweetened beverages, while primarily engaged in another activity, such as watching television.

Dr. Gabriel S. Tajeu, of the University of Alabama, Birmingham’s (UAB) Department of Epidemiology, and colleagues studied data from 28,150 American adults, of whom 55.8% were female, aged from 21-65 years, who participated in the American Time Use Survey between 2006-08.

The investigators assessed time spent on secondary eating and drinking, as well as primary eating and drinking, with sleep duration as the principal independent variable.

They also took into account multiple variables such as race and gender, socioeconomic factors and use of time on weekdays versus weekends, in order to determine the association of short sleep and eating and drinking behaviors. “Normal sleep” was considered to be between 7-8 hours.

Those who reported short sleep also engaged in secondary eating for an additional 8.7 minutes a day, as well as an additional 28.6 minutes daily of secondary drinking on weekdays and 31.28 minutes on weekends.

Other links between obesity and lack of sleep focus on breathing problems and hormonal imbalance.

The US National Sleep Foundation describe sleep apnea, a sleep-disordered breathing condition, as part of a vicious circle. Around 18 million Americans, they say, have the condition, which is often associated with being overweight, because as a person gains weight in the trunk and neck area, respiratory function suffers. The result is daytime sleepiness, making it harder to exercise.

Other studies have shown that building up a sleep debt over a matter of days can impair metabolism and disrupt hormone levels. Studies restricting healthy young adults’ sleep for a few nights have shown that the body’s ability to process glucose in the blood declines, in some cases to the level of diabetes.

Healthy adults who average 6.5 hours of sleep or less have been shown to experience hormonal changes that could affect their future body weight and impair their long-term health. For these people to normalize their blood sugar levels, they would need to make 30% more insulin than normal sleepers. Despite not yet being overweight, these individuals’ profiles predispose them to become so.

The study authors conclude that:

“Short sleep is associated with more time spent in secondary eating and, in particular, secondary drinking. This potentially suggests a pathway from short sleep to increased caloric intake in the form of beverages and distracted eating and thus potential increased obesity risk, although more research is needed.”

Medical News Today has previously reported on the link between lack of sleep and obesity.