How Does Sleep Affect Your Weight?

Several of our internal body systems can go awry without healthy sleep habits, which can affect how our body weight fluctuates. Our metabolic system is responsible for converting food into energy that our bodies can use. When our metabolic system is off balance from a lack of sleep, it can impact both weight gain and loss.
> Understanding the specific relationship between sleep and weight may help motivate and educate you on how to maintain both a healthy weight and healthy sleep habits.

Sleep deficiencies over a prolonged period can negatively affect a healthy metabolism,¹ affecting weight through various biological pathways. In some instances, these pathways intersect and build on each other to affect weight gain even more. Keep reading to learn a few of the ways a lack of sleep can affect your metabolism:

When you’re absolutely exhausted, you may find yourself craving junk food. That’s because when we do not get enough sleep, two hormones that regulate our appetite are affected. The level of leptin, a hormone that makes us feel satisfied when we have had enough to eat, goes down.² At the same time, lack of sleep increases levels of ghrelin, also known as the “hunger hormone.” As a result of these hormonal changes, we may feel hungrier and compelled to eat more than we would if we were well-rested.^{2, 3}

Without enough sleep, our bodies release more cortisol – often referred to as the “stress hormone” - into the blood stream.³ This elevated cortisol slows down the metabolism, impairing our bodies’ ability to convert sugar into energy, and makes it harder to lose weight.

Sleep deprivation causes tiredness, which may hinder physical activity, ultimately decreasing how many calories the body burns throughout the day. It makes sense—when we are tired from a lack of sleep, a 20-minute nap sounds more inviting than a 20-minute cardio routine.

The fatigue and exhaustion that accompany sleep loss aren’t the only reason sleep impacts physical activity. Sleep disturbances can also lead to physiological changes that more directly impact fitness level. In particular, research on the effects of sleep deprivation suggest that sleep is very important for building muscle and using the fuel from our food to increase our strength.

When people experience just one night of sleep deprivation, they may display an impaired ability to build muscle.⁶ Specifically, the synthesis of skeletal muscle protein that our bodies normally undergo after we eat is significantly impaired.^{4, 5}

If you’re not getting enough sleep, your body is tired and trying to find fuel in different ways – affecting how you eat, what you choose to eat, how your body builds muscle mass, and of course, how motivated you are to exercise. So it’s no surprise that those with unhealthy sleep habits are more likely to gain weight than those with healthy sleep habits.

There is an abundance of research showing specifically that those who sleep too little or too much are at a higher risk for weight gain.^{2-3, 6-7}

Even when eating and exercise habits are maintained, research shows that a lack of sleep still increases the likelihood of weight gain.⁸ These findings suggest that sleep influences weight beyond affecting diet and workout habits. So even if you can keep up with a well-balanced diet and exercise routine without sleep—which would be near impossible to do after a period of time—the lack of sleep can still affect weight gain.

Getting less than the recommended 7 to 9 hours of sleep each night for the average adult increases the risk of weight gain.^8-10 The amount of weight gain, however, appears to depend on the extent of sleep deprivation. One study showed that compared to people who sleep at least 7 hours per night, those who sleep only 6 hours per night gain more weight. Further, compared to those who sleep 6 hours per night, those who sleep only 5 hours per night gain even more weight.⁹

Just as sleep deprivation leads to weight gain through its effects on the physiology of our metabolism, our appetites, and our physical activity, it can also impair our ability to lose weight. While there is much more research on the tendency for sleep deprivation to lead to weight gain, there are also some studies that show that poor sleep hygiene makes it harder to lose weight.

For example, a multicomponent weight loss program that included addressing sleep hygiene behaviors led to successful weight reduction, highlighting the importance of addressing sleep when working to lose weight.¹¹

Sleep and weight are inextricably linked through their relationships to metabolism, eating, and exercise. Finding the right balance of nutrition, exercise, and sleep is the best way to promote healthy weight and to protect your overall health.

Establishing healthy sleep habits is essential to your overall health. Promoting a healthy lifestyle goes hand-in-hand with ensuring that you are not only getting enough sleep, but also getting quality sleep.

ZzzQuil is here to help you on your journey to your best sleep. Sign up for ZzzQuil’s Better Sleep in 1-2-Zzz to learn more about how you can optimize your sleep routine.