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Sleep to Lower Body Fat

Getting sufficient sleep on a regular basis can reduce body fat and lower weight

We already know that it’s important to get a solid night of sleep on a regular basis. For the vast majority of people, between six and nine hours is sufficient.

When we don't sleep enough, two hormones in our body are greatly affected: ghrelin and leptin. Ghrelin is a hormone that gives us the "go" signal, meaning that we are hungry and need to eat. On the other end is leptin, a hormone that signals satiety and tells us to stop eating. When we don't get enough sleep, even after just a few short nights of less slumber, the balance between ghrelin and leptin is tipped. We have more ghrelin and less leptin. As a result, the signal that tells us we're full becomes weak, and the "you're hungry, eat!" signal is strengthened.

An interesting November 2013 study, conducted by researchers at Brigham Young University (BYU) and published in the American Journal of Health Promotion, took a somewhat different angle at the sleep/weight connection. Instead of just focusing on quantity of sleep, their research looked at the timing and quality of sleep.

Researchers at BYU investigated over 300 college-aged women over the course of a few weeks, assessing them for body fat composition and keeping track of their sleep patterns for one week. Results showed that participants who obtained less than 6.5 or more than 8.5 hours of sleep per night had higher body fat.

What is novel in this study is their look at the timing of sleep and its impact on body fat composition. The researchers found that a consistent bedtime and, more importantly, wake time, were related to lower body fat. Participants who had more than 90 minutes of variation in their sleep/wake times were more likely to have higher body fat composition than those with less than 60 minutes of variation.

We are all born with internal clocks called circadian rhythms. These rhythms are on a roughly 24-hour clock and keep our bodies in check throughout the day. Not only do circadian rhythms impact our sleep schedules, but they also govern many other complex functions in our body—notably, when hormones are released by various organs in our body. Keeping a fixed wake time seven days per week helps to keep the circadian clock in check all day long. Even though staying with the same bedtime is important, having a constant wake time has many more implications in keeping our body's physiology on the right clock. Plus, not sleeping in allows for us to be out of bed and active for more hours, which helps with lowering body fat.

Finally, the researchers also noted that sleep quality greatly impacted body composition. Participants who slept better had less body fat. A myriad of reasons can factor into why sleep quality might be disrupted: pain, sleep apnea, anxiety, depression, fibromyalgia, etc. And the more disrupted one's sleep is, the more likely they aren't getting all of the benefits of a solid night's sleep. What’s more, less human growth hormone is produced and more of the stress horomone cortisol is released (leading one's body to feel more stressed). These are all things that can impact leptin and ghrelin production, thereby increasing body fat composition.

If you find that you're having trouble logging enough sleep, getting quality sleep, or keeping to a sleep schedule, consider seeing a sleep specialist to help assess any issues that might be contributing to your insomnia.

More from Shelby Harris Psy.D.
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