Sticking to Sleep Schedule Could Help Keep off Fat

Consistent sleep schedule was found to be connected to lower body fat percentage in young adult women

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Both diet and exercise are key to maintaining a healthy weight, but your sleep schedule may be important as well.

A recent study found that women who spent less time awake in bed and had more consistent sleep schedules had a lower body fat percentage than others.

Based on their findings, the authors of this study noted that between 6.5 and 8.5 hours of sleep each night was ideal to have a healthier body weight.

"Get a consistent amount of sleep each night."

This study was led by Bruce Bailey, PhD, of the Department of Exercise Sciences in the College of Life Sciences at Brigham Young University. The research team examined the relationship between consistency of sleep patterns and weight status in young adult women.

Dr. Bailey and colleagues analyzed data from 330 women between 17 and 26 years old who were not dieting, not pregnant or lactating, did not have any metabolic disease and were not taking any medications that affected their metabolism.

The sleep patterns and physical activity of participants were monitored for seven days. The researchers recorded sleep patterns by asking participants to wear a sleep monitor at night. They specifically looked at when participants went to bed, when they woke up, sleep efficiency (the amount of time a participant was asleep over the amount of time they were in bed), changes in bedtime, changes in wake time and changes in the amount of sleep.

The researchers recorded physical activity by asking participants to wear an accelerometer (a device that measures motion) at all times during the seven-day study period except during water activities (e.g., swimming or taking a shower).

The researchers measured body fat percentage (total amount of fat divided by total body weight) and determined body mass index (BMI) — a measure of height and weight. A BMI of less than 18.5 is considered underweight, between 18.5 and 24.9 is considered normal weight, between 25 and 30 is considered overweight, and over 30 is considered obese.

The researchers found that young women who got between 8 and 8.5 hours of sleep had the lowest body fat percentage (24.5 percent) and the lowest BMI (21.9, normal weight) in the study group.

Changes in wake time were found to be the smallest among women who got between 8 and 8.5 hours of sleep (the time they woke up varied by about one hour on average from day to day). Wake time changes were the greatest for women who got under 6 hours of sleep (close to an hour and a half change in wake time on average from day to day).

Women who got less than 6 hours of sleep or more than 8.5 hours of sleep were found to have the highest body fat percentages on average. 

The researchers also found a significant connection between sleep efficiency and body fat percentage. Participants who had greater sleep efficiency (spent less time awake in bed) had a lower body fat percentage on average than women who had lower sleep efficiency.

No connection was found between the time that participants went to sleep or woke up and BMI or body fat percentage. There was also no connection found between length of sleep and BMI.

Based on their findings, the study authors noted that sleep efficiency and a consistent sleep schedule had a greater impact on body fat than sleep duration. They concluded that addressing these factors could prove to be an effective strategy to lower the risk of carrying excess body fat.

This study was published on November 18 in the American Journal of Health Promotion.

The study authors reported no competing interests.

Review Date: 
November 20, 2013
Last Updated:
January 2, 2014