Imagine two days. On one day, you have slept for eight hours; on the other, only five. The food on the table and your workout are exactly the same on both days. Yet on the second day, you may feel hungrier, your cravings for sweets may be stronger, and you may find it harder to stop eating in the evening. This is not necessarily a matter of willpower. Sleep deprivation affects appetite through hormonal, neurochemical, and behavioral mechanisms.
What regulates hunger and satiety?
Ghrelin and leptin are two hormones that communicate with the brain and play a role in regulating hunger and energy balance.
Ghrelin is produced mainly in the stomach and is often referred to as the hunger hormone. Its levels typically rise before a meal and fall after eating.
Leptin is produced mainly in adipose tissue. It provides the brain with information about the body’s energy stores and plays a role in the long-term regulation of appetite and energy expenditure.
One small study involved 12 healthy young men who were allowed to sleep for either four or ten hours on two nights. After the shorter sleep duration, leptin levels were 18% lower on average and ghrelin levels were 28% higher. The participants also rated their hunger and appetite as stronger, particularly their appetite for high-calorie and carbohydrate-rich foods (Spiegel et al., 2004).
This does not mean that everyone experiences exactly the same changes after every night of poor sleep. This was a small, short-term study, but it helped highlight one possible mechanism through which insufficient sleep may affect appetite.
A third hormone that gets less attention: cortisol
Ghrelin and leptin are not the only hormones affected by insufficient sleep. Sleep deprivation puts strain on the body and can also disrupt the normal circadian rhythm of cortisol, one of the main stress hormones. For example, cortisol levels may remain higher in the evening, even though they would normally decrease at that time.
Cortisol does not cause hunger in the same way as ghrelin. However, long-term disruptions in the body’s stress response have been linked to impaired glucose metabolism, reduced insulin sensitivity, and a higher risk of abdominal obesity (Björntorp, 2001).
However, this does not mean that cortisol alone determines where energy is stored in the body or causes fat to accumulate regardless of calorie intake. Body weight and fat distribution are influenced by energy balance, genetics, hormones, physical activity, sleep, and many other factors.
Why crisps rather than chicken?
Sleep deprivation may not only increase overall hunger but may also affect which foods seem most appealing to us at the time.
One study measured levels of the endocannabinoid 2-AG after nights of restricted sleep. It is part of the body’s endocannabinoid system, which is also affected by THC, the psychoactive compound in cannabis. Among other things, the endocannabinoid system helps regulate appetite and the pleasure derived from food.
The study compared the effects of four nights with 4.5 hours of sleep and four nights with 8.5 hours of sleep. After restricted sleep, 2-AG levels rose more in the afternoon and remained elevated for longer. At the same time, participants felt hungrier and found it more difficult to limit their intake of tasty snacks (Hanlon et al., 2016).
Brain imaging studies also help explain this phenomenon. After a sleepless night, activity decreased in brain regions involved in assessing the value of food, while the amygdala response became stronger. At the same time, participants showed a greater preference for high-calorie foods (Greer, Goldstein & Walker, 2013).
A poor night’s sleep can therefore affect hunger, the appeal of food, and the ability to calmly think through our choices all at once. This is why ice cream and a bag of crisps may seem much more tempting than usual when we are tired.
What happens when you start sleeping longer?
Some of the most practical evidence comes from a clinical trial published in 2022. It involved overweight adults who typically slept less than 6.5 hours per night. One group of participants received personalized sleep counseling, but they were not given any dietary or exercise guidance.
As a result of the counseling, the participants’ actual sleep duration increased by an average of about 1.2 hours per night. Compared with the control group, they consumed approximately 270 fewer kilocalories per day on average (Tasali et al., 2022).
This is roughly equivalent to the energy content of an average snack bar. The result does not mean that everyone would automatically consume exactly 270 fewer kilocalories after sleeping longer. However, the study shows that extending sleep may reduce energy intake in some people even without following a specific diet.
Myth: does catching up on sleep over the weekend help?
Many people hope they can catch up on the sleep debt accumulated during the week by sleeping longer over the weekend. While extra sleep may alleviate fatigue, it may not eliminate all the metabolic effects of repeated sleep deprivation.
In one study, participants were divided into three groups. The first group got enough sleep every night, while the second slept for only five hours a night for nine consecutive nights. The third group initially slept for five hours a night for five nights, was then allowed to catch up on sleep without restrictions for two nights, and subsequently slept for five hours a night for another two nights.
Although sleeping longer over the weekend temporarily reduced evening food intake, the participants’ evening energy intake increased and their insulin sensitivity worsened after they returned to short sleep. Therefore, catching up on sleep over the weekend did not fully reverse the effects of the sleep deprivation accumulated during the week (Depner et al., 2019).
This does not mean that catching up on sleep has no benefits. When you are sleep-deprived, sleeping longer is better than continuing to accumulate sleep debt. However, two longer nights may not provide the same benefits as regular, sufficient sleep.
Too little sleep may reduce fat loss
One small study involved ten overweight adults who completed two 14-day calorie-restricted periods. During one period, they were given 8.5 hours of sleep time per night and 5.5 hours during the other.
During both periods, the participants lost approximately the same amount of body weight, but the weight lost came from different tissues. During the shorter sleep period, participants lost 55% less fat and 60% more fat-free mass than during the longer sleep period (Nedeltcheva et al., 2010).
Fat-free mass does not consist solely of muscle. It also includes body water and other non-fat tissues. Therefore, the study does not show that the entire difference was due to muscle mass. However, the result does suggest that adequate sleep may help preserve fat-free mass more effectively during calorie restriction.
Because the study was short and included only ten people, the percentages obtained cannot be applied to everyone trying to lose weight. Nevertheless, the overall message is important: the number on the scale alone does not show which tissues the weight loss came from.
Shopping while tired: do you really choose different foods?
The effects of sleep deprivation may even extend to the foods we choose at the store. One small experiment involved 14 men of normal weight. After a normal night's sleep and after a completely sleepless night, they had to select food items within a fixed budget in a simulated shopping environment.
After a sleepless night, the participants selected foods with 9% higher energy content and 18% more food for their shopping baskets than after a normal night's sleep (Chapman et al., 2013). This shows that acute sleep deprivation can also affect the choices we make at the store.
How can you improve your sleep when life simply does not allow you to sleep more?
People are often advised to simply sleep more to improve their sleep, but it is not always possible to increase sleep duration significantly right away. In that case, it is worth focusing on sleep regularity and quality.
Keep your wake-up and bedtime as regular as possible. This helps support your body's circadian rhythm. Your weekend sleep schedule does not have to be identical to the minute, but very large variations can make waking up on Monday more difficult.
Avoid a very large meal immediately before bedtime. A full stomach, heartburn, or digestive discomfort can interfere with falling asleep and staying asleep.
Be cautious with alcohol. Alcohol may initially make it easier to fall asleep, but it can fragment sleep later and reduce its quality.
Bear in mind the long-lasting effects of caffeine. The half-life of caffeine is often around five hours, but it varies considerably from person to person. An afternoon coffee may therefore affect your sleep at night even if you seem to fall asleep without any problems.
Create a calming evening routine. Dimmer lighting, relaxing activities, and a consistent bedtime help your body begin preparing for sleep.
Frequently asked questions
Can I compensate for sleep deprivation in advance by sleeping longer?
Partly. Sleeping longer before anticipated sleep deprivation may improve subsequent alertness and performance and speed up recovery. However, this does not make sleep deprivation harmless or replace regular, sufficient sleep. So far, there is less evidence on whether sleeping longer also helps prevent hormonal changes.
Can a short afternoon nap help balance hormones?
A 20–30-minute nap may improve alertness, attention, and mood. Its direct effect on ghrelin, leptin, and other appetite-regulating hormones has been studied less extensively. Although a short nap may relieve fatigue, it does not replace sufficient nighttime sleep.
Does everyone have the same hormonal response to sleep deprivation?
No. The strength of the response may depend on age, sex, body composition, genetics, usual sleep patterns, and the duration of sleep deprivation. Scientific studies have also not always produced consistent results regarding changes in ghrelin and leptin. Thus, sleep deprivation may affect appetite, but the strength of the effect and its precise mechanism vary from person to person.
What should you keep in mind in practice?
Take your sleep as seriously as your nutrition. Most adults regularly need approximately 7–9 hours of sleep.
Expect a stronger appetite after a poor night’s sleep. Foods high in calories, sugar, and salt may become particularly tempting. This may be a predictable response from the body, not simply a lack of willpower.
Plan your food choices in advance when you are tired. A shopping list and prepared meals can reduce choices driven by emotions in the moment.
Do not rely solely on catching up on sleep over the weekend. It may improve how you feel, but it may not eliminate all the effects of recurring sleep deprivation.
If you want to lose weight, pay attention to sleep as well. Adequate sleep may support appetite regulation and help preserve lean mass more effectively during calorie restriction.
Try to keep your sleep schedule as consistent as possible. Regularity helps the body’s circadian clock function better, but it does not replace getting enough sleep.
Summary
If your appetite seems much stronger than usual on some days, but there appears to be no clear reason, it is worth considering not only what you have been eating but also how you slept the night before.
Ghrelin, leptin, cortisol, and the endocannabinoid 2-AG are some of the components in the system through which sleep can affect appetite and food choices. Sleep deprivation may also lead to changes in the brain’s response to high-calorie foods, increased fatigue, and a reduced ability to calmly think through your choices.
One night of poor sleep will not harm your health or derail your weight loss. However, if insufficient sleep becomes the norm, maintaining a balanced diet may become more difficult. Sleep is therefore not merely rest but an important part of regulating appetite, metabolism, and body weight.
This article is not a substitute for personalized nutritional or medical advice.
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