effect of fasting on sleep

Do You Need Less Sleep When Fasting?

(Last Updated On: September 19, 2022)

If you’ve just started intermittent fasting, you may feel like you have more energy to work out and perform your daily functions.

You may even complain less about not getting enough sleep or feel like you don’t need the same amount of sleep as you used to. So, do you need less sleep while fasting?

You don’t feel sleepy on fasting days because your body pumps out cortisol (the stress hormone) during your fasted state.

If your blood sugar levels are low or you’re under stress, your body will release more cortisol to convert stored glycogen to glucose, bringing your blood sugar levels back up without eating.

The increased energy while working out is due to the glycogen being converted into glucose. This activates the muscles and enables a fight-or-flight response to a threat.

Since we don’t hunt for food, the excess cortisol adds to our stress load, leading to sleep issues.

How Does Fasting Affect Our Sleep?

Although limiting your food intake for a certain period can benefit your health, intermittent fasting has side effects, especially regarding hormone health. This mainly affects people with adrenal fatigue, thyroid problems, and chemical imbalances.

Sleep deprivation and insomnia are common drawbacks of the chemical imbalances that arise from intermittent fasting, so let’s look closely at the relationship between fasting and sleeping.

Adrenal Hormones (Cortisol)

If you look at it from an evolutionary perspective, intermittent fasting was probably the norm when food wasn’t as readily available as it is now.

There’s a high chance that our paleo ancestors went 12-16 hours without eating regularly and had lighter days when they ate less or nothing.

Therefore, intermittent fasting is part of our evolutionary heritage, but it may not be good for everyone because fasting elevates cortisol levels and vigilance.

Normal Sleep Architecture

This consists of light sleep, deep slow-wave sleep, and REM (dream stage) sleep cycles:

  • Stage 1: This is where you start to doze off, which usually lasts 1-5 minutes.
  • Stage 2: Your heart rate starts to slow, and your body temperature drops.
  • Stage 3: This is the transitional period between light and deep sleep, characterized by 20% to 50% slow brain waves.
  • Stage 4: This includes greater than 50% delta waves and lasts around 30 minutes.
  • Stage 5: This is rapid eye movement or REM sleep, which occurs every 90-110 minutes, with mainly slow-wave sleep taking place in the first half of the night and REM in the second half.

During sleep, the hypothalamus secretes corticotropin-releasing hormone (CRH), which binds with the CRH receptors in the anterior pituitary gland, releasing adrenocorticotropic hormone (ACTH).

ACTH interacts with the adrenal cortex, producing cortisol. Cortisol levels rise within 2-3 hours of sleep and elevate during early morning and waking hours.

Cortisol levels fall by bedtime and increase at night, reaching their peak before you wake up. This acts as a wake-up signal, increasing your appetite and energy levels.

Here’s a summary of the hormones released during sleep and how they affect the body:

  • Growth hormone: For growth and tissue repair.
  • Melatonin: Releases with increased darkness and signals that the body needs sleep.
  • Oxytocin: Peaks after 5 hours of sleep and may influence dreams.
  • Cortisol: Involved in immune response, metabolism, and stress response. Levels rise before waking up to increase hunger and wakefulness in the morning.
long term fasting and sleep

When Does Cortisol Become a Problem?

Throughout your sleep cycle, the body releases cortisol in different amplitudes. High cortisol levels decrease your restorative slow-wave sleep and increase light sleep when the body is stressed, such as during a fasted state.

A common complaint among intermittent fasters is that they frequently wake up at night. In this scenario, your elevated cortisol levels may be responsible. The body produces more cortisol when stressed, blood sugar levels are low, you’ve consumed too much caffeine, etc.

When the body produces high cortisol levels during fasting, the brain can’t tell whether our blood sugar levels are low or we’re in a threatening situation. The brain can’t distinguish between low blood sugar and a potential threat, so it stimulates a stress response.

When the body releases too much cortisol, it produces more adrenaline, resulting in increased wakefulness. However, as the body produces increased amounts of adrenaline, it also results in burnout, resulting in adrenal fatigue and exhaustion. Over time, this cortisol load can cause these health issues:

  • Increased stress and anxiety
  • Depression
  • Increased belly fat
  • Hormonal imbalances
  • Insulin resistance
  • Type-2 diabetes
  • Cardiovascular disease
  • Weight gain
  • Osteoporosis
  • Thyroid issues
  • Digestive issues
  • Chronic fatigue
  • Weakened immune system
  • Fertility issues
  • Sleep problems, such as insomnia

Orexin (Hypocretin)

During fasting, the body releases a neurotransmitter called orexin (hypocretin). Orexin keeps you alert, increases body temperature, makes you want to eat, and elevates the metabolism.

According to the University of Liverpool, low orexin levels in mice are linked to obesity, even when fewer calories are ingested than usual.

Restricting your food intake activates hypocretin cells. Also, anything that stimulates the release of cortisol, such as reduced sleep, will further boost the release of orexin.

This increases your appetite. When you have high orexin levels due to intermittent fasting, you’ll experience difficulty going to sleep because the neurotransmitter increases alertness and wakefulness.

Furthermore, orexin expresses leptin receptors. Studies show that injecting mice with leptin (an appetite-regulating hormone) decreases orexin activity. This shows that orexin is stimulated partly by declining leptin levels in the blood, and an increase in leptin reduces the activation of orexin.

Testing shows that refeeding restores orexin levels back to normal to a certain extent.

What’s the Role of Leptin in Sleep and Obesity?

The less you sleep, the lower your leptin levels. Leptin is an appetite-suppressing hormone, so lower levels may cause you to graze more, increasing your risk of gaining weight.

Furthermore, orexin stimulates your appetite and wakefulness and is activated through the increasing release of cortisol, which in this case, is from fasting.

The only way to feel tired and sleep is to lower your orexin levels by refeeding. This sounds fine, but it may not work for everyone, especially if their bodies are leptin resistant.

Having leptin resistance means the body can’t fully utilize rising levels of leptin after eating again following a fast. People who may be leptin resistant and less likely to respond include anyone:

  • Stressed
  • Coming out of a yo-yo dieting system or severe caloric restriction
  • Insomnia
  • Over-stimulated appetite
  • Underweight due to their low leptin levels
  • Eating disorders, such as binge eating disorder or bulimia
  • Adrenal fatigue

Understanding Leptin Sensitivity

Your body has a “Stop eating” hormone called leptin, which regulates hunger and weight.

Leptin signals to the brain that your energy needs have been met during a meal while controlling your energy expenditure. A well-functioning leptin system improves brain function, performance, memory, mental sharpness, and mood.

However, not taking care of your leptin levels can be a problem, causing leptin resistance. Fortunately, this can be reversed with dietary and lifestyle modifications.

What Causes Leptin Resistance?

Many diets claim that consuming fewer calories and less fat or carbs leads to weight loss.

However, this strategy doesn’t last long. With time, your caloric restrictions lower your leptin levels, slowing your metabolism and making it difficult to lose any excess pounds.

Leptin imbalances can occur when you ignore its “stop eating” signals. Leptin is the hormone that tells you when you’re full—continuing eating in the long-term despite feeling full leads to leptin resistance.

Overeating negatively affects the body’s ability to determine whether fat levels are too high. What’s worse, constantly ignoring your leptin signals can cause the leptin receptors in the brain to become numb, preventing you from feeling full in the future.

Leptin resistance is a red flag for insulin resistance, as leptin is vital in monitoring insulin sensitivity. According to Obesity Research, insulin sensitivity alone can contribute to obesity and type-2 diabetes.

Frequent exposure to stressors and toxins can increase the risk of leptin resistance.

How to Improve Leptin Sensitivity

Short-term fasting can reduce leptin levels. If you’re leptin sensitive, do the following:

  • Have a breakfast high in protein and healthy fats to promote hormone production.
  • Reduce your intake of refined carbs, such as white flour and sugar.
  • Finish eating meals 4-5 hours before bedtime.
  • Consume a diet high in fiber and protein.
  • Increase your intake of anti-inflammatory omega-3 fatty acids, such as avocado, fish, and nuts.

How to Improve Sleep While Fasting

From an evolutionary perspective, our ancestors needed to stay alert for any hunting opportunities. However, the wakefulness that results from intermittent fasting can keep us from falling asleep.

Like most negative effects of fasting, insomnia is worse during the first few days and improves as you continue for several days. However, for some people, insomnia remains an issue during fasting.

If you’re having a hard time falling asleep on fast days, the following strategies are beneficial:

Calories Before Bedtime

Ideally, it would help if you didn’t eat before bedtime, especially during intermittent fasting.

However, consuming high-protein or high-fat snacks like yogurt, warm milk, and cheese can be beneficial if you’re having trouble falling asleep.

Good Sleep Hygiene

Sleep hygiene involves taking the right steps to prepare for sleep, including the following:

  • Avoid looking at a screen close to bedtime. This involves turning off your television, shutting down your computer, and avoiding using your tablet, cell phone, or any other smart device.
  • Keep your bedroom cool and dark. Our bodies are designed to sleep during the night. So, we release more melatonin when it is cool and dark.
  • Use your bedroom for sleep and intimacy only. Don’t use your bedroom for screen-based entertainment, work, hobbies, or anything that requires you to be mentally active.
  • Don’t work out close to bedtime. This increases your alertness and stress, preventing sleep.
  • Avoid sleeping in late in the morning. Instead of trying to take naps and sleeping in extra to make up for lost sleep at night, have a set sleep schedule.
  • Comfortable bedding. Make your bed as soon as you get up. A made bed is more inviting than an unmade bed which can trigger stress and reduces feelings of relaxation.

Morning Sun

Staying in low light indoors can impact your circadian rhythm and the hormones that regulate sleep.

Even a brightly-lit room is no match for the natural brightness of the sun. Getting up and leaving the house for some sun can maintain your biological clock and promote better sleep.

Furthermore, sun exposure promotes vitamin D production in the body, which plays a role in numerous bodily processes, including sleep.

A study by Northwestern University found that individuals who spent more time outdoors during the early morning tended to weigh less.

Why can't I get to sleep when on a fast?

Nutritional Supplements

Some effective sleep supplements include magnesium and melatonin.

Magnesium deficiencies are common, as this mineral plays a crucial role in regulating sleep. Some forms of magnesium are better absorbed than others. For insomnia, magnesium citrate is recommended.

Taking melatonin when fasting can help you get better sleep and reestablish your sleeping patterns. Melatonin is a sleep hormone produced by the body to support sleep.

Don’t shy away from smaller doses, such as 0.5 mg. You can increase your dosage slowly if a lower dose doesn’t is ineffective. Work your way up to 3-5 mg, if required.

Tryptophan Foods

Turkey is rich in tryptophan, an amino acid that promotes serotonin and melatonin production.

Foods containing tryptophan include poultry, eggs, cheese, pumpkin seeds, sesame seeds, mung beans, and kidney beans.

Reduced Glucose Levels

Following a heavy meal, your blood sugar levels spike, which stimulates the release of insulin to bring blood glucose levels back to normal.

Usually, the increased surge of insulin causes blood sugar to drop lower than normal, resulting in an energy crash and increased sugar cravings.

If hunger and increased cravings keep you awake, avoid blood glucose fluctuations throughout the day. To do this, avoid adding too many sugars, artificial sweeteners, and refined carbs to meals.

Avoid high glycemic foods and increase your protein, good fats, and fiber intake. Adding protein or healthy fats will lower the glycemic value and increase your satiety if you crave something sweet.

No Coffee After Midday

Caffeine remains in your system for up to 8 hours, countering the effects of melatonin.

Stop drinking high-caffeine beverages after noon to prevent caffeine from keeping you up at night. Drink a caffeine-free alternative, such as coconut water, if you require a quick boost.

Shorter Naps

Sleep deprivation during fasting stages at night may increase your urge to nap more in the daytime. However, taking long, frequent naps can throw off your natural circadian rhythm.

The solution is to take one short nap. Have a set nap time for any day you need a quick energy boost. Our alertness level dips between 1 pm to 3 pm, so take naps at this time.

Keep naps to 10-15 minutes. When you sleep for longer than 20 minutes, you enter deeper stages of sleep. Awakening from deep sleep can leave you feeling groggy and lethargic.

Intermittent fasting alone won’t resolve body weight, blood sugar, or inflammatory issues. Not taking the right steps to improve your sleep and optimize your fasting can prevent you from enjoying the benefits of this lifestyle.

Practice the right sleep techniques while incorporating measures to keep your leptin sensitivity in check. Allow your body to rest, and include quality protein and good fats from fish, avocado, olive oil, and nuts to promote the healthy production of sleep-promoting hormones.