When it comes to weight loss, diet and exercise are two of the biggest topics of conversation. People are constantly searching for the best diet, and hitting the gym to help “burn off” the pounds, however, sleep is one of the most commonly forgotten pieces of the puzzle. Although diet and exercise are certainly some of the most important factors in weight loss, sleep is actually just as important, if not more.
Why does sleep matter?
The first and most obvious reason why sleep matters for weight loss is because the amount of sleep you get directly affects how much food you put in your mouth. If you are tired you are more likely to reach for extra food during the day, and if you are staying up late at night you are more likely to snack, likely out of boredom, and consume extra calories.
However, the second and more influential reason why sleep affects weight loss is hormones. Lack of sleep and poor quality sleep contributes to hormone imbalances in insulin, leptin, cortisol, and many other hormones, which have a profound impact on weight.
The Weight Loss Hormone Link
Insulin is a hormone produced by the pancreas that helps to regulate the levels of glucose in our bloodstream. Every time that you eat, insulin works as the bloodstream’s “traffic controller” to determine how much glucose (sugar) should be used as fuel and how much should be stored for later (as body fat). Insulin regulates the body’s ability to manage carbohydrates, determining what to use and when, while leptin works alongside insulin to let the brain know when we have eaten enough. However, lack of sleep can increase both insulin and leptin levels causing the body to become desensitized to their response. What that means is that insulin is more likely to store food as fat, and due to the reduced sensitivity in leptin, you are more likely to still be hungry after eating.
Lack of sleep and poor quality sleep has also been shown to affect the body’s natural cortisol levels. Cortisol is one of our primary stress hormones that help to manage our energy levels. In a normal state, cortisol levels should be high in the morning, peak mid-morning, and begin to slowly decline throughout the day, being at their lowest point at bedtime. However, studies show that poor sleep habits can lead to disrupted cortisol levels creating low morning cortisol levels (when it should be at its highest) and high evening cortisol levels (when it should be at its lowest). Because lack of sleep is a form of stress on the body, cortisol responds to help the body manage this stress response, however, this becomes problematic for weight gain given chronically elevated cortisol levels lead to increased insulin. So, in basic terms, every time you undersleep or have poor quality sleep, you contribute to elevated cortisol levels which increase insulin levels, which tells the body to store more food as fat.
Hormones, Behaviors, and Cravings
Not only do these changes in hormones heavily affect how your body manages, burns, and stores fat, but they affect your general behaviors as well. When you are tired, you are quite simply more likely to reach for more food during the day in an effort to help keep yourself energized. That typically means extra sugary snacks and extra cups of coffee which, in turn, both further perpetuate the cycle of disrupted insulin, leptin, and cortisol.
Moreover, when sleep-deprived, research shows that we are more prone to want to stimulate the reward center of our brain. Dopamine is a neurotransmitter responsible for managing the reward-motivation center of our brain, and lack of sleep contributes to a lack of control over this center. So, with lack of sleep, we not only crave more junk foods as a reward but have less control and motivation over these cravings. Not to mention, high cortisol levels can lead to reduced serotonin levels (your feel-good neurotransmitter that affects your appetite) so you become more likely to reach for treats for an emotional boost.
The Bottom Line
Weight loss is not as simple as the “calories in, calories out” equation it is made out to be. You can be doing everything right, but if you are getting by on 5 hours of sleep every night you are simply sabotaging your hard work. So, if you are trying to lose weight, but are struggling to move the needle, make sure that you are getting some much-needed shut-eye to support the process.