Sleeping And Fasting: Is It Possible To Do Both?

Sleep is an essential part of our lives, and getting the right amount of quality sleep is crucial for our health and well-being. While most people need at least seven hours of sleep per night, some individuals may require more or less depending on various factors. Oversleeping, or long sleeping, is defined as regularly sleeping for more than nine hours in a 24-hour period. This can be a result of sleep debt, where an individual is catching up on lost sleep, or it could indicate an underlying health condition such as hypersomnia, a condition characterized by excessive daytime sleepiness.

Fasting, on the other hand, has gained attention for its potential benefits, including weight management and improved metabolic health. It involves abstaining from food and sometimes beverages for a specified time and has been practiced for cultural, religious, and health reasons. Some researchers suggest that fasting may also impact sleep quality and duration, with potential effects on the body's internal clock or circadian rhythm.

So, can someone sleep all day and still fast? The answer is yes, as fasting is about abstaining from food rather than the activities one engages in. However, it's important to note that both sleep and fasting are complex processes that can vary from person to person and may be influenced by individual factors such as age, lifestyle, and health conditions. Additionally, while occasional oversleeping may be due to sleep debt, regularly sleeping all day could indicate an underlying health issue, and it's essential to consult a healthcare professional for personalized advice.

Fasting may help align your circadian rhythm and improve sleep quality

Circadian rhythm fasting is a form of time-restricted feeding (TRF) that involves eating all of one's food across a span of hours in the earlier part of the day. This practice can help synchronize one's appetite with their circadian rhythm and improve their metabolism. Circadian rhythm fasting falls under the umbrella of intermittent fasting but prioritizes an earlier eating window during the day.

The human body follows a 24-hour circadian rhythm, or daily cycle, driven by a master clock in the brain and influenced by external factors like light and food. Circadian rhythms govern a range of functions, from sleep-wake cycles and body temperature to hormone levels and digestion.

Disruptions to the body's natural circadian rhythm can lead to sleep issues, fatigue, and more serious health consequences like cardiovascular disease. Intermittent fasting can be a useful tool to help maintain this rhythm and improve sleep quality.

By abstaining from food during the evening and nighttime, intermittent fasting may strengthen the body's circadian rhythm and improve sleep quality and duration. This type of fasting is particularly beneficial for individuals with erratic sleep patterns.

Additionally, intermittent fasting promotes a shift towards fat-burning, which is essential for high-quality sleep. It also affects the production of hormones like melatonin and human growth hormone (HGH), which play a crucial role in regulating sleep.

However, it is important to note that the research on the effects of fasting on sleep is still evolving, and the impact may vary depending on individual factors such as age, gender, and health conditions. While fasting may be beneficial for some, it is not suitable for everyone, including children, individuals with eating disorders, and those with certain metabolic disorders.

To optimize sleep while intermittent fasting, it is recommended to practice good sleep hygiene, maintain proper hydration, limit exposure to blue light before bed, and incorporate meditation or relaxation techniques.

Fasting can have different impacts on different people

Fasting has gained attention for its potential benefits in weight management and metabolic health. It involves voluntarily abstaining from food and sometimes beverages for a specified time. While it has been practiced for centuries, often associated with cultural and religious traditions, its potential physiological benefits are now being explored.

Some researchers suggest that the timing and nature of our eating habits significantly impact our sleep. According to sleep scientist Dr. Carleara Weiss, "Intermittent fasting with limited food intake in the evening and nighttime may strengthen circadian rhythm and improve sleep quality and duration." Fasting may also positively impact the gut microbiome, which is linked to better sleep. Additionally, fasting can affect hormone production, such as boosting ketone bodies, which act as an alternative energy source for the brain during low carbohydrate intake.

However, it's important to note that the research on fasting and sleep is mixed, and conclusive evidence is limited. Some studies suggest that fasting can reduce rapid eye movement (REM) sleep, potentially having negative effects. Additionally, individuals with certain conditions, such as eating disorders, metabolic disorders, or those who are pregnant or breastfeeding, should exercise caution or avoid fasting altogether.

The impact of fasting on sleep can vary from person to person, and it's always best to consult with a healthcare provider before starting any fasting regimen. While fasting may offer benefits, most people are more likely to improve their sleep by focusing on sleep hygiene practices, such as maintaining a consistent sleep schedule, creating a relaxing bedtime routine, and limiting blue light exposure before bed.

Fasting may affect your hormones and influence sleep regulation

Fasting may affect your hormones and, in turn, influence your sleep regulation. Fasting can boost the production of ketone bodies, which are molecules made by the liver as it breaks down fats from your diet. Ketone bodies act as an alternative energy source to glucose, especially for your brain, during times of very low carbohydrate intake or fasting.

Some research suggests that an increase in ketone bodies may influence brain chemicals and hormones involved in sleep regulation. However, this is not yet well understood.

Fasting may also affect the production and secretion of insulin, which is a major metabolic hormone. Insulin stimulates glucose uptake and storage of excess energy as glycogen and lipids in target tissues such as skeletal muscles and adipose tissues. Insulin also inhibits glucose production in the liver, thereby lowering postprandial blood sugar to maintain normal blood glucose levels.

Fasting for 24 hours in mice decreased plasma insulin levels dramatically and abolished the normal circadian rhythm compared with mice that ate their fill. Similarly, studies in mice that fasted every other day for three months and 20 weeks, respectively, reported a dramatic reduction in serum insulin levels by the last week of the diet.

In humans, intermittent fasting decreased plasma insulin levels and improved insulin sensitivity. This change has already been observed during acute fasting. For example, upon 72-hour fasting, plasma insulin dropped by about 35% during the first 24 hours and reached half of baseline levels by the end of fasting.

Fasting may also affect the production and secretion of thyroid hormones, which promote thermogenesis in brown adipose tissue and accelerate lipolysis in white adipose tissues. Fasting for 24 hours lowers serum T3, which might result from increased activity of type III deiodinase, which inactivates thyroid hormones.

In humans, the T3 level starts to decrease rapidly after fasting. When measured during 80-hour fasting in healthy subjects, marked T3 and TSH reductions were observed within 48 hours from fasting onset. Another trial reported that serum T3 decreased by up to 55% after 24 hours of fasting.

Fasting may also affect the production and secretion of glucocorticoids, which stimulate the breakdown of macromolecules and counter-regulate insulin to maintain glucose homeostasis. They also induce anti-inflammatory responses and cardiovascular hypertonicity.

The circadian control of blood glucocorticoid levels occurs through multiple mechanisms, including hormonal cascades in the HPA cortex axis, autonomic neural signals, and local clocks residing in the adrenal cortex. Neural projections from the suprachiasmatic nucleus to the hypothalamic paraventricular nucleus activate the release of corticotropin-releasing hormone, which stimulates the pituitary to secrete adrenocorticotropic hormone, which finally induces glucocorticoid secretion from the adrenal gland.

When rats experience 24-hour fasting, the corticosterone peak is delayed by two hours. Several time-restricted feeding studies commonly reported that the peak time of corticosterone moved to the time when feeding started.

For humans, cortisol begins to increase immediately after fasting commences. Five-day fasting increases cortisol levels and shifts the peak from the morning to the afternoon. Other fasting experiments for 2.5 to 6 days dramatically elevate plasma cortisol levels.

Fasting may also affect the production and secretion of growth hormone, which is produced by the anterior pituitary gland and promotes the growth of lean body mass and lipolysis. Fasting for six hours in mice or 72 hours in rats dramatically decreases plasma growth hormone levels, which might be caused by decreased growth hormone-releasing hormone or increased somatostatin after food deprivation.

In humans, fasting for 37.5 hours elevates basal growth hormone concentrations by tenfold and reduces the metabolic clearance rate of growth hormone. Other studies reported that the frequency of the growth hormone cycle increased, and growth hormone peaks were observed even during the daytime after two- or five-day fasting.

Fasting may also affect the hypothalamus-pituitary-gonad axis, which controls the female reproductive cycle. A 12-week alternate-day fasting in rats disrupted the four-day estrous cycle. Compared with control females, fasting rats showed abnormally increased estradiol and significantly decreased luteinizing hormone. Another fasting study in rats for 30 weeks also showed an increased risk of an irregular or absent estrous cycle.

Fasting may also affect the production and secretion of melatonin, which is derived from tryptophan and secreted from the pineal gland. Melatonin synchronizes the body to the central circadian cycle and starts to increase at the onset of darkness, peaking between 2:00 a.m. and 4:00 a.m.

In humans, three-day fasting causes an acrophase advance by 81 minutes, but neither the maximal level nor the overall circadian pattern is changed. During Ramadan fasting, the peak of plasma melatonin is lower, but its circadian rhythm remains unchanged. These findings indicate that the melatonin circadian rhythm is mainly regulated by the light/dark cycle rather than the feeding pattern.

Fasting may not be suitable for those with certain medical conditions

• Children and Adolescents: Growing bodies have unique nutritional requirements, and fasting may impact their growth and development. Fasting is not generally recommended for those under 18 years of age.
• Pregnant or Breastfeeding Women: Fasting during pregnancy or breastfeeding may deprive the body of essential nutrients necessary for fetal development and lactation. It is not recommended for pregnant or breastfeeding individuals.
• Individuals with Eating Disorders: Fasting can potentially trigger or exacerbate unhealthy eating behaviours and may not be appropriate for those recovering from or at risk of eating disorders.
• Individuals with Diabetes: Fasting can lead to dangerous spikes and crashes in blood sugar levels, especially for those with type 1 diabetes who take insulin. It is not recommended for those with diabetes who require multiple insulin injections per day.
• Individuals with Metabolic Disorders: Conditions such as hypoglycaemia (low blood sugar) may be aggravated by fasting.
• Athletes: Athletes and individuals who engage in multiple hours of daily training require a constant supply of calories to support their activity levels and recovery. Fasting is not recommended for those looking to optimise athletic performance.
• Individuals with Unstable Medical Conditions: Fasting is not recommended if your medical condition is unstable. This includes individuals who are unwell and require a blood transfusion or IV fluids.

It is important to consult with a healthcare professional before starting a fast to ensure it is safe and appropriate for your individual circumstances.

Improving sleep hygiene habits can help reduce excessive sleepiness

• Set a sleep schedule: Try to sleep and wake up at the same time every day, even on weekends. This reinforces your body's sleep cycle and can make it easier to fall asleep and wake up.
• Follow a bedtime routine: Develop a relaxing bedtime routine such as taking a warm bath, doing gentle stretches, meditating, or listening to soothing music. Start your routine 30-60 minutes before bedtime and stick to it consistently.
• Disconnect from electronic devices: Blue light from electronic devices can interfere with melatonin production, making it harder to fall asleep. Unplug from all devices at least 30 minutes before bedtime.
• Exercise regularly: Aim for at least 30 minutes of aerobic exercise daily. Exercising outdoors in natural light can further regulate your sleep cycle. However, avoid intense exercise close to bedtime as it may hinder your ability to settle down.
• Limit caffeine intake: Caffeine can keep you wired even when you want to rest. Limit your caffeine consumption to the morning or early afternoon, depending on your sensitivity.
• Optimise your bedroom: Make sure your bedroom is comfortable and inviting for sleep. Maintain a cool temperature (around 65-68°F or 18-20°C), use comfortable bedding, and block out light and noise with curtains, eye masks, earplugs, or white noise machines.
• Reserve your bed for sleep and sex: Using your bed only for sleep and sex strengthens the mental association between your bed and sleep, making it easier to fall asleep. Avoid activities like reading or working in bed.
• Relax before bed: If you're not tired, avoid tossing and turning in bed. Instead, do something relaxing until you feel sleepy, then go to bed. If you can't fall asleep within 20 minutes, get up and do a calming activity in low light before trying again.
• Limit napping: Napping during the day can disrupt your sleep schedule. If you must nap, keep it short (around 20 minutes) and in the early afternoon.
• Manage stress: Write down your worries and to-do lists before bed to clear your mind. Try meditation or deep breathing exercises to calm your mind and body.
• Avoid large meals, alcohol, and nicotine before bed: Eating a large meal before bed can disrupt your sleep and cause acid reflux. Alcohol and nicotine can also negatively impact your sleep quality.

Frequently asked questions