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Most public health campaigns focus on the importance of diet and exercise for maintaining a healthy weight, but adequate sleep may be just as essential. A large proportion of the population is both overweight and voluntarily sleep-deprived, and there seems to be a strong connection between the two. A meta-analysis published in the journal Sleep combined data from 45 studies with a total of 634,511 participants and concluded that there is a consistent increased risk of obesity amongst short sleepers. Adults who got less than five hours of sleep per night were 55 percent more likely to be obese than those who slept for 7 to 8 hours.
Lack of sleep affects your brain and body in ways that lead to increased hunger, cravings for calorie-dense food and decreased physical activity. If you get less than 7 hours of sleep on a regular basis and are struggling to lose weight, going to bed earlier might be the key to weight-loss success. Here are seven ways that a lack of sleep can cause weight gain.
You may have noticed that you feel hungrier and tend to snack more when you're sleep deprived. These cravings for food are due to the effect of sleep on hormones that signal hunger or fullness. The hormone leptin regulates appetite, metabolism and calorie burning. It signals to your brain that your body has enough energy to run on and that you don't need to immediately find something to eat. Leptin levels naturally increase while you are sleeping. If you get too little sleep, your body has a shortage of leptin the following day. Lower levels of the 'fullness hormone' can lead to constant cravings, especially for high-calorie foods.
Ghrelin is another hormone associated with sleep deprivation and weight gain. Ghrelin balances leptin by sending hunger signals to the brain. Levels are normally high when the stomach is empty and low when it is full. A lack of sleep causes the stomach to release more ghrelin the following day. Higher levels of the 'hunger hormone' can lead to an increase in appetite and a tendency to consume more calories at meals and snack times. The combination of too much ghrelin and too little leptin is a recipe for weight gain.
Sleep deprivation affects regions of the brain associated with the reward value of food, decision-making and self-control. These neurological changes can make unhealthy snacks seem more appealing, while simultaneously reducing our ability to resist them. In one study, researchers at Columbia Universityscanned the brains of 30 men and women after six nights of normal sleep and six nights where sleep was restricted to four hours. The participants were shown pictures of food or non-food items during the brain-scanning sessions. Sleep deprivation increased activity in brain regions associated with motivation to seek out food as a reward.
When you've had less than 7 hours of sleep, other regions of the brain show changes that can influence your relationship with food. The emotional center of the brain, the amygdala, becomes more active and more sensitive to negative feelings. Simultaneously, the prefrontal cortex, which governs rational thought, becomes less active. When you're tired, you're both more emotional and more impulsive, making you more likely to consume unhealthy comfort foods.
Lack of sleep causes an increase inghrelin levels combined with increased activity in the reward centers of the brain, both of which contribute to cravings for high-calorie foods. A Swedish study published in the journal Obesity investigated the effect of sleep deprivation on food purchasing choices. On the morning after either sleep deprivation or eight hours sleep, participants ate breakfast then shopped in a mock supermarket. They were given coins worth approximately 50 US dollars and instructed to spend them all on 40 possible food items. After a night of sleep-deprivation, the participants purchased 18 percent more grams of food with 9 percent more calories compared to what they bought after a good night's sleep.
Sleep deprivation causes feelings of fatigue which may reduce your motivation to exercise. In a study published in The American Journal of Clinical Nutrition, 15 men were given devices to wear on their wrists which recorded daily activity and sleep/wake patterns. After sleeping either 4 or 8 hours in a lab, they were free to leave and go about their daily business. Men who got only 4 hours of sleep reported feeling weak and tired. Sleep restriction significantly decreased their overall spontaneous physical activity during the day and also decreased the intensity of activities they engaged in.
In the hours between dinnertime and bedtime, many people snack on high-calorie junk food while engaging in sedentary pastimes such as watching television or playing video games. In a society where convenience food is available 24/7, people who spend more time awake and inactive are likely to consume more calories. According to one estimate, published in the journal Obesity Reviews, replacing one hour of TV watching with sleepingwould reduce daily calorie intake by about 6 percent and lead to a weight loss of approximately 14 pounds over the course of a year.
The physical, mental and emotional changes that come with lack of sleep make it difficult to follow any healthy eating plan, much less a low-calorie diet. Too little sleep affects your ability to make good decisions about what to eat in the spur of the moment or what to buy at the supermarket. It may be tempting to stay up late watching the streamed box-set of your favorite drama or catching up with social media, but committing to a healthy lifestyle means making adequate sleep a top priority. If you want to lose weight, aim for 7 to 8 hours of quality sleep every night.
By A.C. Anschuetz