Sleep has been getting a lot of attention this year as a factor in body composition regulation. Now, another study is claiming that people who get less sleep on average are more likely to be obese.

The study found that:
Although there is wide variation, there are significant differences in mean sleep time between certain BMI categories.
Gender is an important factor in explaining the relationship between sleep and BMI.
Overall, people with higher BMIs had less sleep, but the increase in weight and sleep is more closely related in women than men.
Among adults in the BMI range of 18.5 to 40, women get 20 minutes more sleep per night than men on average.
The largest difference in sleep time was seen between Class I and Class II obese groups of males, with a decline of 11 minutes for men in Class II. (Class I = BMI of 30-34.9; Class II = BMI of 35-39.9)

According to Robert F. Kushner, M.D., co-investigator and clinical director of The Northwestern University’s Comprehensive Center on Obesity: “This study represents an important advancement in the study of sleep and how it is impacted by a person’s weight and the different effect it has on males and females. People looking to lose weight often take into account calorie consumption and physical activity levels, two very important factors; however, new research like this can play an important role in the obesity dialogue to help educate people interested in losing weight about the role of sleep.”

Overall, BMI is still used as a measurement tool in many studies. This study would be more interesting if body composition and body fat percentage were compared to sleep hours instead of BMI. Body Mass Index is a problematic measure of obesity for a number of reasons, including failure to take into account high bone density and a high amount of lean muscle mass. Still, study after study has shown a similar link between a shorter sleep duration and obesity.

How many hours of sleep do you get per night?