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Possible Link Between Late Bedtimes and Weight Gain

Last updated Oct. 5, 2015

Approved by: Maulik P. Purohit MD MPH

What happens when you don't sleep? And why do we need to do it anyways? Hank Green from Vlog Brothers explains the science of sleep: the cause, the benefits, and who holds the record for going without it!


A team of researchers from University of California, Berkeley and Columbia University, New York, find from a recent study, a correlation between late bedtimes and increase in body mass index.

The body mass index or BMI, is calculated based on an individual’s height and weight, is indicative of whether that person’s weight is “healthy.” A BMI of less than 24.9 is considered normal, whereas a value over 25 and 30 is deemed overweight and obese, respectively. Research has focused on understanding the reasons for the recent weight gain “epidemic.” Not only could weight gain be traumatic on the psychological front, but it also brings with it innumerable health problems, such as type-2 diabetes, sleep apnea, high blood pressure, and resultant heart problems.

One of the contributory factors to obesity has been recognized as poor quality of sleep. Sleep is considered an important modulator of hormonal functions, which are disturbed when children and adults do not sleep long enough. The importance of getting enough sleep during the night in maintaining a healthy body weight has been emphasized in a number of research findings. The current study explores the link between the time one actually goes to bed and weight gain.

In a nationally representative sample, the research team examined the relationship between bedtime and weight gain. Data obtained from 1994-2009 of 3342 adolescents in The National Longitudinal Study of Adolescent Health was used to analyze and assess their bedtimes and BMI. The results of the analyses are:

  • Later average bedtime during the workweek resulted in an increase in BMI over time.
  • A sleep deficit of 1 hour as a consequence of late bedtimes resulted in a gain of 2.1 points on the BMI scale, over a period of approximately five years.
  • This increase in BMI remained significant after adjusting for baseline BMI and demographic traits.
  • Exercise or the number of hours an individual slept did not reduce the increase in BMI owing to late bedtime.
  • Fast food contributed to the weight gain owing to late bedtimes.

Most adolescents experience a delay in their sleep phase, shifting their circadian rhythms (the biological clock that operates in a 24-hour cycle and regulates sleep-wake cycle). The results of this study are significant for the future health of adolescents. Commenting on the importance of going to be early, the lead author states in the Berkeley News, that this habit will “set their (the adolescents’) weight on a healthier course as they emerge into adulthood.”

The authors suggest that bedtimes could be a potential target for effective weight management during adolescence and transition into adulthood. The finding makes one think about the expression “Early to bed and early to rise makes a man healthy, wealthy and wise.” Maybe our forefathers knew what they were talking about.

Written by Mangala Sarkar, Ph.D.

Primary References

Asarnow, L., Mcglinchey, E., & Harvey, A. (2015). Evidence for a Possible Link between Bedtime and Change in Body Mass Index. Sleep, 38(10), 1523-1527.

Late bedtimes could lead to weight gain. (2015, October 1). Retrieved October 2, 2015, from http://news.berkeley.edu/2015/10/01/late-bedtimes-bmi/

Additional References

Do You Know Some of the Health Risks of Being Overweight? (n.d.). Retrieved October 2, 2015, from http://www.niddk.nih.gov/health-information/health-topics/weight-control/health_risks_being_overweight/Pages/health-risks-being-overweight.aspx

Obesity: MedlinePlus. (n.d.). Retrieved October 2, 2015, from https://www.nlm.nih.gov/medlineplus/obesity.html

Cauter, E., & Knutson, K. (2008). Sleep and the epidemic of obesity in children and adults. European Journal of Endocrinology, 159(S1), S59-S66.

Bayon, V., Leger, D., Gomez-Merino, D., Vecchierini, M., & Chennaoui, M. (2014). Sleep debt and obesity. Annals of Medicine, 46(5), 264-272.

Karatsoreos, I., Bhagat, S., Bloss, E., Morrison, J., & McEwen, B. (2011). Disruption of circadian clocks has ramifications for metabolism, brain, and behavior. Proceedings of the National Academy of Sciences, 108(4), 1657-1662.

Sleep Drive and Your Body Clock. (n.d.). Retrieved October 2, 2015, from https://sleepfoundation.org/sleep-topics/sleep-drive-and-your-body-clock

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Oct. 5, 2015
Last updated: Oct. 5, 2015