The amount of sleep you get may be just as important for weight loss as your diet and exercise. Evidence shows that sleep may be the missing factor for many people trying to lose weight.
The Undervalued Role of Sleep in Weight Management
When it comes to weight loss, diet and exercise are usually thought of as the two key factors that will achieve results. However, sleep is an often-neglected lifestyle factor that also plays an important role.
Many people aren’t getting enough sleep. According to the Centers for Disease Control and Prevention (CDC), 39% of adults sleep fewer than 7 hours most nights, which is considered short sleep. Sleep has a wide range of benefits on physical and mental well-being, but a lesser-known benefit is its support in maintaining a moderate weight.
How Too Little Sleep Impacts Your Weight
Not getting enough sleep is linked to higher rates of obesity. Most adults need seven to nine hours of sleep most nights. People who consistently log six or fewer hours tend to have a higher body mass index (BMI). And even just a few nights of short sleep can result in short-term weight fluctuations.
Not getting enough sleep can also increase your glucose (blood sugar) levels. That raises your risk of Type 2 diabetes and obesity.
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And while it may seem obvious, a lack of sleep leaves you feeling tired. That lack of energy can make you less inclined to be active or get any type of exercise. When not sleeping means more time on the couch and less time at the gym, you may find yourself struggling to maintain your weight.
The Link Between Sleep Duration and Weight Gain
Short sleep, usually defined as fewer than 6 to 7 hours, has been repeatedly linked to a higher body mass index (BMI) and weight gain.
One analysis of 20 studies including 300,000 people found a 41% increased obesity risk among adults who slept fewer than 7 hours per night. In contrast, sleep was not a factor in the development of obesity in adults who slept longer, at 7 to 9 hours per night.
A 2018 review of many observational studies found short sleep duration was associated with a significantly higher risk of obesity in these different age groups:
- Infancy: 40% increased risk
- Early childhood: 57% increased risk
- Middle childhood: 123% increased risk
- Adolescence: 30% increased risk
Though lack of sleep is only one factor in the development of obesity, 2018 research suggests it negatively affects hunger levels, influencing a person to consume more calories from high fat and high sugar foods.
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Sleep's Impact on Appetite-Regulating Hormones
Sleep quality affects two important hormones that regulate appetite - leptin and ghrelin.
Leptin is often called the “satiety hormone” because it’s the one that signals your body to feel full after a meal. Ghrelin has the opposite effect. It stimulates your appetite and makes you feel hungry.
When you consistently get a good night’s sleep, your body regulates these two hormones and makes sure they stay in the proper balance. But when you are chronically sleep deprived, leptin levels decrease and ghrelin levels increase. The result: You feel hungrier before a meal and less satisfied afterward - which can lead to junk food cravings and overeating.
It may do this by affecting hunger hormone levels - increasing ghrelin, which makes you feel hungry, and decreasing leptin, which makes you feel full.
Ghrelin is a hormone released in the stomach that signals hunger in the brain. Its levels are high before you eat, 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.
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When people do not get adequate sleep, their bodies make more ghrelin and less leptin, which leaves them hungry and increases their appetite.
Poor sleep may also negatively affect the sympathetic nervous system, resulting in increased levels of cortisol, a hormone related to stress.
Sleep Deprivation and Food Cravings
In addition to changes in hormones that impact how much you eat, sleep deprivation can also affect what you eat. Experts don’t know exactly why not getting enough sleep makes you turn to less healthy food, but there are some possible explanations.
One theory is that when you’re tired you simply have less energy to devote to healthy eating. You may not feel like taking the time and effort to shop for and prepare nutritious meals. Or you may have less willpower to drive past the bakery or fast-food place without stopping for a high-calorie treat.
Some recent research has found a connection between sleep and the chemicals that make up the reward system in the brain. When you’re sleep-deprived, you may crave foods that feed into that reward system.
For example, a 2019 study found that sleep-deprived participants had greater reward-related brain responses after viewing images of high calorie foods. They were also more likely to pay more for food than those who had adequate sleep.
This means that after a night of inadequate sleep, not only is that bowl of ice cream more rewarding, but you’ll likely have a harder time practicing self-control.
Lack of sleep alters the way your brain works and can affect decision making. This may make it harder to form healthy food choices and prioritize nutrition-dense meals.
It also appears that food stimulates the brain’s reward centers more when people are sleep deprived.
Poor sleep can decrease your self-control and decision making abilities, as well as increase your brain’s reaction to food. Poor sleep has also been linked to an increased intake of foods high in calories, fats, and sugar.
The Impact of Late-Night Eating
If you’re not getting enough sleep every night, you’re likely to be hungry at some point between dinner and bedtime.
Late-night eating is associated with greater weight gain, a higher BMI, and decreased fat oxidation, making weight loss more difficult.
What’s more, eating too close to bedtime, especially large meals, may decrease the quality of your sleep and make your sleep deprivation even worse. In particular, anyone with acid reflux, indigestion, or sleep disorders may want to limit food intake before bed.
Ideally, try to limit your food intake 2 to 3 hours before bed. That said, if you’re hungry, consider having a small, protein-rich snack, such as Greek yogurt or cottage cheese.
Poor sleep can increase your calorie intake by increasing late-night snacking, portion sizes, and the time available to eat.
Sleep, Metabolism, and Fat Oxidation
Getting enough sleep may help you avoid metabolic decreases that can occur when you aren’t getting enough sleep.
Lack of sleep may also suppress fat oxidation, which is the breakdown of fat cells into energy. The researchers explain that this suppression may result from the activation of the body’s stress system.
Poor sleep may affect your metabolism and your body’s ability to break down fat cells into energy.
The Interplay Between Sleep and Physical Activity
Sleep and physical activity have a close two-way relationship. A lack of sleep decreases physical activity, and a lack of physical activity may lead to worsened sleep.
Numerous studies have shown that regular exercise can decrease the time it takes to fall asleep and increase the overall quality of sleep across all age groups.
A lack of sleep can also cause daytime fatigue, making you less motivated to exercise and more likely to be sedentary.
In turn, sleep-deprived people may expend fewer calories in a day than they would after a proper night’s rest. This can make achieving a calorie deficit for weight loss more difficult.
What’s more, a lack of sleep can negatively affect your athletic performance by decreasing your:
- reaction time
- fine motor skills
- muscular power
- endurance
- problem-solving skills
It may also increase your risk of injury and delay recovery.
Ultimately, getting enough sleep is key to staying active.
Getting enough sleep may increase your motivation to be more active and enhance your athletic performance, both of which can contribute to weight loss. Interestingly, being physically active can also improve your sleep.
Prioritizing Sleep for Successful Weight Loss
If you’re trying to lose weight, not getting enough sleep can make it more challenging.
A lack of sleep is linked to less nutritious food choices, increased hunger and calorie intake, decreased physical activity, and ultimately, weight gain.
If your weight-loss efforts aren’t producing results, it could be helpful to examine your sleep habits. When you’re trying to manage your weight, your first focus is likely on what you eat. It’s true that weight management requires a focus on healthy foods and limited intake of sugary, high-calorie, high-fat foods.
Exercise can also be an important tool. Staying physically active helps you burn more calories. It can also help ensure that you maintain muscle.
But there’s a third factor that can be key to weight management, and it’s often overlooked. Turns out that how well you sleep plays an important role. Sleep affects many of your body’s functions. And that, in turn, impacts your motivation, your blood sugar levels and your food choices.
The Importance of Sleep Quality
Yes, slow-wave sleep, often called deep sleep, is a key marker of sleep quality. This stage of sleep helps with memory consolidation, restoration at the cellular level and tissue repair, and the clearing out of metabolic waste products. It also has an important role in metabolism and hormonal release. For example, a major pulse of growth-hormone secretion occurs during slow-wave sleep.
Our experimental work4 has shown that if you deprive healthy young adults of slow-wave sleep - to the levels seen in older adults, or in people with sleep apnoea - they show signs of prediabetes after just three days. This finding opened up an area of research that focused on the role of sleep quality in diabetes risk. And data emerging from large population studies suggest that adults who get sufficient slow-wave sleep have a lower future risk of developing diabetes. So finding ways to get enough slow-wave sleep seems to be important, particularly for younger people.
Tips for Better Sleep
Consistent lack of sleep can lead to conditions ranging from heart disease and diabetes to cancer.
To give yourself the best shot at a good night’s sleep, create healthy sleep habits:
- Avoid late-day caffeine
- Keep electronic devices (phones, tablets, computers) out of the bedroom
- Keep your bedroom cool, dark and quiet
- Limit alcohol intake before bed
- Maintain a regular schedule of bedtime and wake-up time
- Practice relaxation rituals (a warm bath, herbal tea, meditation, yoga) to help you mentally unwind before bed
The basics are pretty simple: