Which is More Important for Weight Loss, Exercise or Sleep?

New research finds that for weight loss, healthy sleeping habits likely play an important role

New research published in the journal Sleep found that when compared with those who achieve adequate amounts of sleep, sleep-restricted adults may be more prone to weight gain due to a larger daily caloric intake.

In order to analyze the effects of sleep restriction on “weight gain, daily caloric intake, and meal timing,” researchers at the University of Pennsylvania followed 225 healthy, non-obese men and women. The subjects were between the ages of 22 and 50 and were split evenly and randomly between two groups: the sleep-restricted group or the control group.

The study took place in the Sleep and Chronobiology Laboratory at the Hospital of the University of Pennsylvania over the course of as many as 18 days.

According to the American Council on Exercise (ACE), members of the sleep-restricted group were only allowed four hours of sleep per night for five consecutive days, while the control group members were allowed to sleep for 10 hours each night.

During the course of the study meals were served at scheduled times, but there was also additional food available to subjects, which they could eat whenever they wanted. The subjects could participate in sedentary activities like watching TV or reading, but none were permitted to exercise.   

The results: the sleep-restricted group gained more weight than the subjects in the control group.

The researchers concluded that the sleep-restricted group’s weight gain was due to a greater daily caloric intake, with more meals consumed late at night and a greater percentage of those late-night calories coming from fat.

“Although previous epidemiological studies have suggested an association between short sleep duration and weight gain/obesity, we were surprised to observe significant weight gain during an in-laboratory study,” the study’s lead author Andrea Spaeth, a doctoral candidate in the psychology department at the University of Pennsylvania, told ACE.

When it comes to comparing healthy habits that promote weight loss and prevent weight gain, the study’s results don’t necessarily prove whether one might be “more important” than the other, but more so that lacking in one area—sleep especially, can significantly hinder your efforts in another.

What’s more, in addition to its association with weight gain, insufficient sleep—which the Centers of Disease Control and Prevention has dubbed a “public health epidemic”— is associated with a slew of other health risks such as cardiovascular disease, diabetes, and impaired immunity.

This particular study, as ACE noted, adds to the growing body of research that shows why it’s not enough to only focus your efforts on exercise and emphasizes the importance of maintaining an overall healthy lifestyle (which includes healthy sleeping habits).