Sleep and Metabolism

While it may seem a waste of time to spend a third of your life sleeping, your body and your mind engage in essential restorative functions every night. DNA is repaired, toxins are cleaned up, muscles and bones regenerate and your mind processes the activities that occurred during the day.

Recent studies have linked sleep restriction of less than 7 hours per night to weight gain. In a large study of 14,000 people, the most fit got the most sleep. Fitness was defined by both BMI and waist circumference. Optimal sleep was defined as 7-9 hours. Surprisingly, those who slept more than 9 hours were even more fit than those who slept the recommended 7-9 hours per night.

In another study, sleep restriction predisposed teenagers to the development of obesity and increased waist circumference. This is an important finding because we are seeing a steady increase in metabolic illness, including obesity and diabetes, in young people. It is not uncommon for young adults to be sleep deprived due to staying up late and getting up early for school. These findings suggest that sleep is a modifiable factor in disease risk for people of all ages.

Getting enough sleep is important for our wellbeing but when we sleep also has a huge impact on health. Sleep cycles are naturally controlled by environmental triggers and social cues including daylight, artificial light, meal times and timing of exercise/activity. Of these triggers, light-dark cycles have the greatest impact. When it gets dark at night our brains produce the hormone melatonin. Melatonin induces sleep, has antioxidant capacity and improves insulin sensitivity.

People who work at night are prone to diabetes even when they get a full 8-10 hours of sleep during the day. One study of night nurses showed a decrease by as much as 17% in glucose tolerance at 8 PM as compared to 8 AM. Lower glucose tolerance is associated with insulin resistance, an early stage of diabetes.

The importance of these finding is that good health is impacted by much more than simply nutrition and exercise. Altering your daily rhythm to be more aligned with the day-night cycle can be a powerful way to regain and maintain your health.

Sources

Ford ES, Li C, Wheaton AG, Chapman DP, Perry GS, Croft JB. Sleep duration and body mass index and waist circumference among U.S. adults. Obesity (Silver Spring). 2014 Feb;22(2):598-607. doi: 10.1002/oby.20558. Epub 2013 Oct 15. PMID: 23836704; PMCID: PMC4580243.

Quante M, Mariani S, Weng J, Marinac CR, Kaplan ER, Rueschman M, Mitchell JA, James P, Hipp JA, Cespedes Feliciano EM, Wang R, Redline S. Zeitgebers and their association with rest-activity patterns. Chronobiol Int. 2019 Feb;36(2):203-213. doi: 10.1080/07420528.2018.1527347. Epub 2018 Oct 26. PMID: 30365354; PMCID: PMC6492024. 

Morris CJ, Yang JN, Garcia JI, et al. Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans. Proc Natl Acad Sci U S A. 2015;112(17):E2225-E2234. doi:10.1073/pnas.1418955112