Lack of sleep can have a counterintuitive effect on living a full, healthy lifestyle. It is not news that sleep deprivation is associated with obesity, and some of the reasons as to why are obvious. A greater number of hours awake equate to a greater number of hours where you’re able to open the fridge. Additionally, the typical sleep deprived 9 to 5-er repeatedly lives the old adage of planning on going to the gym right after work, but by the time they get to the end of their shift, they are so exhausted they can barely manage to make themselves dinner and get to bed. We all know that sleep is important, but it is much more intricately involved in hunger and obesity than is seen at face value.
Sleep and Satiety Hormones
There are two main satiety hormones, leptin and ghrelin. (There are others including PYY, but ghrelin and leptin are the primary ones.) Leptin is famous for being the hormone that makes you feel full, and ghrelin is notorious as the hormone that makes you feel hungry. The release of leptin by adipose cells is mainly triggered by meal intake; circulating leptin is usually at its lowest point in the morning and slowly increases over the day to its peak at night time shortly before going to bed. Ghrelin is released by the stomach on a more on and off basis, rapidly decreasing after a meal and increasing in anticipation of the next meal. Both of these hormones work in sync to control satiety and hunger throughout the day.
Both ghrelin and leptin are very connected to how much and how long you sleep. Quite interestingly, during the second half of the night when one might expect ghrelin to be very high and leptin to be very low after not having eaten for several hours while asleep, the opposite happens. Ghrelin levels drop and leptin levels remain high, likely to prevent hunger awakening you in the middle of the night.
When sleep patterns are disrupted, ghrelin and leptin are disrupted as well. This is true whether you lack sleep for one day, or chronically for weeks or months. During a state of sleep deprivation, ghrelin levels are increased and leptin is decreased more than usual. This leads to a state in which you feel hungry even when your body does not need to eat. One study in particular showed that after only six days of sleeping four hours per night, leptin levels had decreased to a level that was equivalent to after three consecutive days of restricting calories back by 900kcal/day with normal sleep. Additionally, it is more likely that the foods you crave the most are those that are high in simple sugars, because your body desperately craves the quick burst of energy that sugar provides. For this reason, sleep deprivation has been proposed as the third most likely contributing factor to obesity, following poor diet and lack of physical activity.
The CDC recommends that adults get at least 7-9 hours of sleep per night. Whether you are looking to lose weight, or just generally want to live a healthy life, sleeping well should be just as important to you as getting in your daily workout.
Additional Resources:
Leproult, Rachel, and Eve Van Cauter. “Role of Sleep and Sleep Loss in Hormonal Release and Metabolism.” Endocrine development 17 (2010): 11–21. PMC. Web. 18 May 2018.