Skip to main content

The Globe and Mail

How sleep affects your 'fat genes' - and your 'fat jeans'

Jacob Wackerhausen/iStockphoto

Lack of sleep not only makes you cranky and accident prone – it may also put your "fat genes" into high gear, a new study suggests.

"The less sleep you get, the more your genes contribute to how much you weigh. The more sleep you get, the less your genes determine how much you weigh," lead author and neurologist Nathaniel Watson told USA Today.

Dr. Watson and colleagues at the University of Washington Medicine Sleep Center in Seattle looked at the height, weight and sleep habits of 604 pairs of identical twins and 484 sets of fraternal twins. After analyzing the data, they reached the following conclusions:

Story continues below advertisement

  • Individuals who slept longer at night had lower body mass index (BMI) than those sleeping less.
  • For twins who got more than nine hours of sleep a night, genetic factors accounted for about 32 per cent of weight variations.
  • For twins who averaged less than seven hours, 70 per cent of weight variations were due to genetic factors.

Dr. Watson noted that both BMI and the need for sleep are inherited traits. Even so, "we see differences in how much twins weigh based on their sleep duration," he said.

That doesn't mean people can sleep themselves thin, Dr. Watson told the Huffington Post. "But you can sleep yourself to a point where environmental factors, like diet and activity, are more important in determining your body weight than genetics."

The research may seem at odds with a 2008 study showing a link between excess sleep – more than nine hours a night – and obesity. But researchers of that study, conducted by the U.S. National Center for Health Statistics, found that nearly half of people who slept nine hours or more each night were physically inactive in their leisure time, and many had serious health problems.

Dr. Watson and his co-authors acknowledged that more than 20 genes are involved in regulating energy use, fat storage, appetite and the body's ability to process glucose.

Still, "there is an amount of sleep where people become less healthy," Dr. Watson told ABC News. "Most people need between 7 and 9 hours a night."

How many hours of sleep do you get a night? Do you put on weight when you're sleep deprived?

Report an error Licensing Options
About the Author

Adriana Barton is based in The Globe and Mail’s Vancouver bureau. Her article on growing up with counterculture parents is published in a McGraw-Hill anthology, right after an essay by Margaret Atwood. She wishes her last name didn’t start with B. More

Comments are closed

We have closed comments on this story for legal reasons. For more information on our commenting policies and how our community-based moderation works, please read our Community Guidelines and our Terms and Conditions.

Combined Shape Created with Sketch.

Combined Shape Created with Sketch.

Thank you!

You are now subscribed to the newsletter at

You can unsubscribe from this newsletter or Globe promotions at any time by clicking the link at the bottom of the newsletter, or by emailing us at privacy@globeandmail.com.