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Sleep & weight: what's the connection?

Updated: Jul 1, 2023

When it comes to losing weight, most people focus on diet and exercise. While those are certainly important, other factors can significantly influence our weight loss efforts. One such factor is sleep.

Did you know that when we snooze, our brains are still at hard work? As we peacefully slumber, our brains enter a state of tranquility, cycling through various stages of activity, while our muscles can be relaxed or even locked into a state of deep paralysis. According to research, good sleep plays a key role in maintaining a healthy metabolism and optimal energy balance through various hormonal and metabolic processes. When we get insufficient sleep, our metabolism can suffer, potentially leading towards weight gain and other health related issues.

Let's explore the relationship between the body's rest cycle and weight.

Uncovering the Link Between Sleep Deprivation and Hunger

There is a strong correlation between lack of sleep and hunger. Researchers from The University of Pennsylvania found that a reduction in sleep duration, on a regular basis, increases daily food intake by an average of 300-550 kcal/ day. Their research looked at differences in energy intake and weight gain between individuals with poor sleep quality versus those with good quality sleep. Study participants with fewer hours of sleep at night preferred foods rich in calories, high in carbohydrates and they ate during late night hours; as a result, they gained weight.

To better understand the relationship between sleep deficit and hunger, researchers then looked at changes in appetite hormone levels. Although many hormones may have a role in appetite control, the most studied ones are leptin, "the fullness hormone", and ghrelin, "the hunger hormone". When leptin levels are high, you feel satisfied and don't feel the need to eat more. When levels of ghrelin are high, this signals hunger, and need for more food.

An analysis of studies investigating the connection between sleep and the levels of hormones involved in appetite regulation, yielded mixed results. According to some experts, an elevation in ghrelin levels and a decrease in the levels of leptin would explain why we feel hungry after a night of insufficient rest. Per others, the changes were not significant enough to account for the effect. Additional research is necessary to arrive at a definitive answer.

It has also been postulated that levels of endocannabinoids increase sharply after a night of poor sleep. These substances are produced naturally by our bodies and can lead to an increase in food cravings and calorie consumption.

Take away point: Lack of proper sleep not only increases how much you eat as a result of hunger, but changes your food preferences. Hunger leads to an increase in energy intake.

Lack of sleep may increase insulin, glucose and stress hormones levels

Did you know that one of the secrets to shedding those extra pounds lies in the delicate balance between your insulin, glucose, and stress hormone levels? Insulin is the hormone that controls the amount of glucose in the blood. When insulin levels are low, the body can use its fat stores to produce the energy it needs. Anything that raises blood glucose will result in an increase in insulin which then converts glucose into stored energy in the form of fat, making it harder to lose weight.

There are metabolic changes that occur inside us when we don't get sufficient sleep. Most notably:

  • Our bodies respond less to insulin. This is also known as having a decreased insulin sensitivity. As a result, we produce more insulin to overcome this barrier. This extra hormone will more efficiently convert the available glucose into fat stores.

  • Sleep architecture changes. Particularly, researchers noticed a decrease in slow-wave sleep patterns, which results in an increase in sympathetic nervous system activity. The sympathetic nervous system is a network of nerves in your body that is responsible for activating the "fight-or-flight" response to help us survive in high stress situations. While very helpful for our survival, the excess activation of these neurons has been linked to an increase in glucose levels, leading to a higher risk for diabetes.

  • Levels of cortisol go up! Cortisol is a hormone that regulates sleep and is known as the body's main stress hormone. When we're stressed, cortisol increases blood sugar and fat storage while lowering insulin sensitivity. Poor sleep leads to high cortisol levels, according to clinical trials. And cortisol in excess leads to weight gain over time.

Take away point: Maintaining low glucose and insulin levels, and managing stress, can be helpful in achieving weight loss.

Does sleep duration affect how our brain perceives food?

Sleep loss may alter our brain response to food and can lead to impulsive eating habits. In a study conducted by experts from Columbia University, a group of study participants were observed under two conditions: sleep-deprived and well rested. After each condition, they were shown different types of food and asked to rate their desire for each food item while being scanned inside an MRI machine.

This study found that sleep restriction had a significant impact on the brain, causing it to shift to a pattern of activity associated with compulsive eating. The "prefrontal cortex," which is responsible for impulse control, was shut down. In the meantime, the "primitive deep brain regions" that drive excessive appetite, became hyperactive and hyper-responsive to highly desirable foods. This led the people included in the study to choose carbohydrate rich foods and to increase their fat intake and salt intake instead of making healthier food choices such as increasing their fruit intake or vegetable intake. The conclusive evidence is that fewer hours of sleep per night changes how our brain perceives food, and can become a risk factor for weight gain.

Observational studies conducted in Sweden showed that healthy people exposed to experimental sleep restriction were more likely to make unhealthy food choices and eat larger portions resulting in an increased protein calorie intake per day. In another study, participants purchased foods with significantly more calories after a night of total sleep deprivation than after a night of good rest.

Take away point: When we're tired, we make less smart food choices, eat in excess and can have a harder time losing weight. On the flip side, an increase in sleep duration helps improve self-control with regards to food. Don't grocery shop when tired, make a healthy choice!

Poor sleep equals less weight loss

Research has shown that insufficient sleep makes it difficult to lose weight. While staying up all night minimally increases energy expenditure, it does not counteract the increased hunger resulting in higher daily calorie intake. When tired, we are also less inclined to exercise thus our physical activity level is reduced.

Moreover, a high percentage of the weight lost when sleeping fewer hours per night, comes from fat free mass, like muscle, instead of fat. Our body composition changes as a result of metabolic and neuroendocrine compensation mechanisms which together result in decreased energy expenditure leading our bodies to store "food" as fat. During periods of limited food intake, lack of sleep can lead to an increased loss of fat-free body mass due to the body converting protein into glucose to support the brain and other tissues. Over time, this results in weight gain and development of obesity.

Take away point: For successful weight loss, good sleeping habits are paramount.

Timing matters, even for sleep

Our body's natural clock otherwise known as the "circadian rhythm" is involved in maintaining our weight. In this regard, researchers unanimously agree that disrupting this rhythm increases the risk of health conditions, most of which are chronic diseases such as obesity, diabetes, and cardiovascular disease. Shift workers, who often have irregular sleep schedules, are particularly at risk. Even "social jetlag," when our sleep patterns differ on weekends compared to weekdays, has been linked to obesity.

Research shows that later bedtimes and wake times are linked to more sedentary behavior and less physical activity. So, paying attention to our body clock, and maintaining a regular schedule can be an essential factor for achieving healthy body weight.

Keeping your food intake hours in sync with the circadian clock, can prevent excess weight gain, while eating at odd hours can have the opposite effect. This highlights the importance of paying attention to meal timing in relation to our body's natural rhythms when it comes to developing healthy eating habits.

Take away point: Listen to and obey your body's natural rhythms regarding eating and sleeping.

Sleep is important. What can I do now?

Design your personal sleep routine! The following suggestions may help:

  1. Make sure your bedroom is dark, quiet, and cool. This will help you fall asleep faster and stay asleep throughout the night.

  2. Avoid caffeine or alcohol intake close to bedtime. Additionally, If you smoke, consider quitting as it can also interfere with a good restful night.

  3. It's important to shut off screens 1-2 hours before bedtime, as the blue light emitted by electronic devices can interfere with your body's natural sleep-wake cycle. Shut off your screens 1-2 hours before bedtime.

  4. Try not to nap for more than an hour or in the late afternoon, as this can make it harder to fall asleep at night.

  5. Practice regular exercise or be physically active throughout the day.

  6. Keep the bedroom for sleeping only.

  7. Eating a healthy diet and avoiding eating too close to bedtime, can also contribute to better sleeping.

  8. Most importantly, stick to a regular bedtime routine, even on the weekends.


Adequate sleep is important for maintaining an optimal weight and provides numerous other health benefits.

Chronic sleep deprivation can increase the risk of obesity as it disrupts the body's endocrine function and affects dietary intake. When tired, we make less healthy food choices, and lack motivation to exercise, resulting in a negative impact on our physical health and an increase in waist circumference. Better sleeping on the other hand, can help regulate our appetite and maintain a healthy body composition.

Making good rest a priority as part of a healthy lifestyle is considered a "behavioral weight loss intervention" for those looking to successfully lose weight. So, if you're struggling with weight management, consider focusing on improving your sleeping habits. You may very well see an increase in your energy levels, and a whole host of other wonderful benefits.

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