Sleep Loss & Weight Gain: Genetic or Behavioral?

There is growing evidence linking chronic sleep loss with an increased risk of obesity. Short sleep durations are associated with higher body mass index (BMI) scores.

What is the nature of this relationship? Is it genetic? Environmental? Behavioral?

A new study provides some intriguing insight. The results were published last month in the Journal of Clinical Sleep Medicine.

The study surveyed 612 pairs of twins. Each pair was raised together in the same household.

They had an average age of about 37 years. They reported their height, weight and habitual sleep duration.

Results show that 25 percent of participants reported sleeping less than seven hours per night. These short sleepers had a higher average BMI (26.0) than those with a typical sleep duration of seven to 8.9 hours per night (24.8).

An adult with a BMI of 18.5 to 24.9 is considered to be at a “normal” weight. An adult who has a BMI of 25 to 29.9 is considered to be “overweight.”

The results were confirmed in an analysis of 423 monozygotic pairs. Each of these twin pairs shares 100 percent of their genetics. Short sleepers again had a higher BMI (25.7) than normal sleepers (24.7).

There also were 245 twin pairs that differed in their sleep durations. An analysis of these pairs also produced similar results. The shorter-sleeping twins had a higher BMI (25.8) than the twins who had a typical sleep duration (24.9).

How strong was the genetic influence on sleep duration? Further analysis produced a modest heritability estimate of 31 percent for sleep duration. In comparison, the heritability estimate for BMI was 76 percent.

There was little evidence of shared genetics between sleep duration and BMI. Common environmental factors also appeared to have little influence on the link between sleep and BMI.

The results support the idea that voluntary sleep restriction affects BMI. This effect appears to be independent of familial factors.

Do you know your BMI? Use the BMI Calculator on the left side of the blog to find out.

Read more about sleep and obesity and sleep and weight gain.

Image by Jodi Green