1. Poor Sleep Is a Major Risk Factor for Weight Gain and Obesity
Poor sleep has repeatedly been linked to a higher body mass index (BMI) and weight gain, especially those who get fewer than seven hours of sleep a night.
A major review found that short sleep duration increased the likelihood of obesity by 89% in children and 55% in adults.
2. Poor Sleep Can Increase Your Appetite
Many studies have found that people who are sleep-deprived report having an increased appetite. This is likely caused by the impact of sleep on two important hunger hormones, ghrelin and leptin.
Ghrelin is a hormone released in the stomach that signals hunger in the brain. Levels are high before you eat, which is when the stomach is empty, and low after you eat.
Leptin is a hormone released from fat cells. It suppresses hunger and signals fullness in the brain.
When you do not get adequate sleep, the body makes more ghrelin and less leptin, leaving you hungry and increasing your appetite.
A study of over 1,000 people found that those who slept for short durations had 14.9% higher ghrelin levels and 15.5% lower leptin levels than those who got adequate sleep.
3. Sleep Helps You Fight Cravings and Make Healthy Choices
Lack of sleep actually alters the way your brain works. Sleep deprivation will actually dull activity in the frontal lobe of the brain. The frontal lobe is in charge of decision-making and self-control.
In addition, it appears that the reward centers of the brain are more stimulated by food when you are sleep deprived. Therefore, after a night of poor sleep, not only is that bowl of ice cream more rewarding, but you’ll likely have a harder time practicing self-control.
A study of 12 men observed the effects of sleep deprivation on food intake. When participants were only allowed four hours of sleep, their calorie intake increased by 22%, and their fat intake almost doubled, compared to when they were allowed eight hours of sleep
4. Poor Sleep Can Increase Your Calorie Intake
People who get poor sleep tend to consume more calories.
A study of 12 men found that when participants were allowed only four hours of sleep, they ate an average of 559 more calories the following day, compared to when they were allowed eight hours.
Poor sleep can also increase your calorie intake by affecting your ability to control your portion sizes.
This was demonstrated in a study on 16 men. Participants were either allowed to sleep for eight hours, or kept awake all night. In the morning, they completed a computer-based task where they had to select portion sizes of different foods.
The ones who stayed awake all night selected bigger portion sizes, reported they had increased hunger and had higher levels of the hunger hormone ghrelin.
5. Poor Sleep May Decrease Your Resting Metabolism
Your resting metabolic rate (RMR) is the number of calories your body burns when you’re completely at rest. It’s affected by age, weight, height, sex and muscle mass.
In one study, 15 men were kept awake for 24 hours. Afterward, their RMR was 5% lower than after a normal night’s rest, and their metabolic rate after eating was 20% lower.
It also seems that poor sleep can cause muscle loss. Muscle burns more calories at rest than fat does, so when muscle is lost, resting metabolic rates decrease.
One study put 10 overweight adults on a 14-day diet of moderate calorie restriction. Participants were allowed either 8.5 or 5.5 hours to sleep. Both groups lost weight from both fat and muscle, but the ones who were given only 5.5 hours to sleep lost less weight from fat and more from muscle
6. Sleep Can Enhance Physical Activity
A lack of sleep can cause daytime fatigue, making you less likely and less motivated to exercise.
A study done on 15 men found that when participants were sleep-deprived, the amount and intensity of their physical activity decreased (22).
The good news is that getting more sleep may help improve your athletic performance.
In one study, college basketball players were asked to spend 10 hours in bed each night for five to seven weeks. They became faster, their reaction times improved, their accuracy increased and their fatigue levels decreased.
7. Poor Sleep Can Cause Cells To Become Insulin Resistance
Insulin is a hormone that moves sugar from the bloodstream into your body’s cells to be used as energy. When cells become insulin resistant, more sugar remains in the bloodstream and the body produces more insulin to compensate.
The excess insulin makes you hungrier and tells the body to store more calories as fat. Insulin resistance is a precursor for both type 2 diabetes and weight gain.
In one study, 11 men were allowed only four hours of sleep for six nights. After this, their bodies’ ability to lower blood sugar levels decreased by 40%).
This suggests that only a few nights of poor sleep can cause cells to become insulin resistant.