Does Going to Bed Too Late Cause Weight Gain?

Mom working late in bed
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The importance of getting enough sleep cannot be overstated when it comes to your health—and that starts with bedtime.

Later Bedtime, More Weight Gain

Recent research has found that teenagers or young adults who go to bed late on weeknights are more likely to gain weight over time.

In a study of nearly 3,500 adolescents who were followed between 1994 and 2009 in the National Longitudinal Study of Adolescent Health, researchers looked at how bedtimes affected body mass index (BMI) over time.

The study authors found that a “later average bedtime during the workweek, in hours, from adolescence to adulthood was associated with an increase in BMI over time.” The researchers noted that consumption of fast food in particular seemed to be playing a role in the relationship between bedtimes and BMI.

This finding does not appear to be limited to teenagers and young adults. In another study, researchers found that late bedtimes, and therefore less nightly sleep, for 4-year-old and 5-year-old children resulted in a greater likelihood of obesity over time. Specifically, the researchers found that the odds of becoming obese were higher for children who slept less than about 9.5 hours per night, as well as for children who went to bed at 9:00 p.m. or later.

Health Benefits of Sleep

A plethora of studies in adults have reflected similar results. Most studies have shown that seven to nine hours of uninterrupted sleep per night are required to reap the health benefits of good sleep in adults, including those related to preventing obesity.

In addition to preventing obesity and overweight, getting enough high-quality sleep every night can help prevent heart disease, stroke, depression, and other chronic disorders. When we sleep, the body gets a chance to repair and restore itself. If it does not have enough time to do this over the long-term (chronically), then stress hormones and other inflammatory factors are released, as the body begins to react as if it were under chronic stress (which, without enough sleep, it is).

One of the main players in terms of stress hormones is cortisol, which is released in response to chronic stress.

Among many other of its influences on the body, cortisol causes glucose (sugar) to be released into the bloodstream so that it is more readily available to feed the brain. As an evolutionary response to chronic stress, this probably worked quite well, enabling a person under stress to respond with more brain power. However, in today’s world, an unwanted side effect of cortisol’s actions is the tendency for weight gain (makes sense that our ancestors would need to store or hold onto weight if they were truly under stress from a harsh environment). That weight gain, over time, can translate into obesity.

Indeed, studies have shown that lack of adequate sleep can result in overeating. And for those who are trying to lose weight, getting enough sleep (again, at least seven hours per night) increases the chance of success with weight loss.

For children, as shown by the studies described above, the amount of sleep needed is even greater, sometimes 10 or more hours per night, depending upon age.


Asarnow LD, McGlinchey E, Harvey AG. Evidence for a possible link between bedtime and change in body mass index. Sleep 2015;38:1523-7.

Scharf RJ, DeBoer MD. Sleep timing and longitudinal weight gain in 4- and 5-year-old children. Pediatr Obes 2015;10:141-8.

St-Onge M, O’Keeffe M, Roberts AL, RoyChoudhury A, et al. Short sleep duration, glucose dysregulation and hormonal regulation of appetite in men and women. Sleep. 2012;35:1503-10.

Elder CR, Gullion CM, Funk KL, DeBar LL, et al. Impact of sleep, screen time, depression and stress on weight change in the intensive weight loss phase of the LIFE study. International Journal of Obesity. 2012;36:86-92.

Bonow RO, Mann DL, Zipes DP, Libby P. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Ch. 79. Elsevier: Saunders, 2012.

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