Home » Nutrition » 10 Intermittent Fasting Side Effects That You Need To Know Before You Follow It

10 Intermittent Fasting Side Effects That You Need To Know Before You Follow It


Fasting is a common habit preferred by some individuals to lose weight. Fasting helps an individual by lowering the calorie intake creating a calorie deficit in the body.

Hence, calorie deficiency leads to a loss of body weight. But, do you know that people practice multiple ways of fasting depending on their needs and capacity?

Intermittent fasting is one such method where people prefer to create a calorie deficiency and ensure essential nutrient intake in their bodies.

In this article, I have tried to discuss the side effects of practicing intermittent fasting on healthy individuals.

Intermittent Fasting Side Effects

  1. May Increase Hunger And Cravings

    Naturally, you may feel hungry as soon as you reduce your calorie intake.

    You get a specific window or timing to consume your daily calorie requirements in intermittent fasting.

    But, it may not be possible for an individual to eat enough food to sustain the remaining hours of the day without food.

    Moreover, during intermittent fasting, your body may quicken the digestion process due to less food intake, which may increase hunger.

    The side effects may exist until your body adapts to your new eating pattern. Generally, your body may take weeks to adjust to the latest changes.

    Hence, you may feel hungry during the initial few days of practicing intermittent fasting.

  2. May Lower Blood Sugar Level

    In a few people, intermittent fasting may increase the chances of hypoglycemia.

    Hypoglycemia is the condition referred to as the drop in the blood sugar level below a healthy range.

    If you experience frequent headaches or dizziness during intermittent fasting, it may signify a falling blood sugar level.

    Moreover, skipping morning meals could negatively impact[1] blood sugar levels for a diabetic person.

    Hence, it is advised for people with insulin or thyroid problems to practice intermittent fasting cautiously.

    A healthy individual may experience a drop in low blood sugar levels, but it could be temporary.

    The body takes time to adjust to an imbalance in sugar levels, which may get regular after a few days.

  3. May Get Frequent Headaches

    Intermittent fasting may increase the frequency of headaches in some people.

    It is believed that due to reduced food consumption, you may start to experience a rapid fall in blood glucose level or hypoglycemia.

    Moreover, intermittent fasting may induce caffeine withdrawal in the body which could be the reason for headaches.

    The fasting headaches get very common with intermittent fasting as it asks for 16 or more hours of fasting.

    You may experience mild or moderate fasting headaches in the brain’s frontal region.

    The headache frequency could be higher in people suffering from migraines than in those who don’t.

    But, the headache may go away as soon as you start consuming food and beverages.

  4. May Cause Orthorexia – An Eating Disorder

    Intermittent fasting restricts you from having desired food at desired times.

    You need to follow several rules that may help you get the intermittent fasting results.

    But, a few people take these rules an extra mile which could potentially lead to an eating disorder called orthorexia.

    Due to intermittent fasting’s strictness, some people spend a hefty amount of time thinking about the quality and quantity of food.

    Hence, the increased focus on the correctness of food could impact the individual’s overall health.

    It is essential to develop a healthy and positive relationship with the food to get the highest benefits from food.

    But, due to increased focus on restricted eating habits, you may be stuck with eating disorders.

    Additionally, it would be best to avoid intermittent fasting if you previously had eating disorders.

  5. May Cause Multiple Digestion Problems

    Sudden changes in the diet plan and eating habits may lead to multiple digestion problems.

    Intermittent fasting asks to change the eating pattern and food to lead a healthy and fit lifestyle.

    But, immediate changes may cause some digestive issues like bloating, diarrhea, nausea, or constipation in the initial days.

    As you practice intermittent fasting, you start to eat fewer calories or food. You may suffer from constipation due to the drop in food intake.

    Also, the fasting process could lead to dehydration which may worsen constipation if you are also avoiding water during the fast.

    Hence, it is advised to eat fiber and nutrient-rich food and drink plenty of water during the days of intermittent fasting to avoid digestive issues.

  6. May Cause Hair Loss

    Intermittent fasting could be a reason for your hair loss as it creates risks for deficits of essential nutrients like Vitamin B, some proteins, etc.

    Generally, people practicing intermittent fasting fail to consume all the essential macro and micronutrients during the eating hours.

    Hence, they may experience increased hair loss after starting intermittent fasting.

    Additionally, intermittent fasting promotes a hair condition called telogen effluvium- a type of temporary hair loss.

    People suffering from telogen effluvium may experience thinning, weakening, and hair loss.

    Moreover, they may notice a sudden increase in hair fall after beginning intermittent fasting.

    But, it isn’t a matter to worry about, as telogen effluvium is a temporary hair condition that could be treated by consulting doctors.

  7. May Experience Changes In Menstrual Cycle

    Whether a woman increases or decreases her weight, she may experience a sudden change in the menstrual cycle.

    In the case of intermittent fasting, a woman may not get enough calories to undergo menstruation, hence, a random or stopped menstrual cycle could be seen.

    If a woman sheds excessive weight due to intermittent fasting, she may be prone to amenorrhea (absence of menstruation).

    Moreover, intermittent fasting could cause a hormonal imbalance that plays a significant role in irregular periods.

    Hence, if you are practicing intermittent fasting and experiencing such side effects, you may consult a dietitian or change the meal plan or may also add some fruits to your diet to fill the nutritional gap.

  8. May Cause Mood Swings

    Sometimes the fasting habit may lead to multiple moods or mood swings in an individual.

    Especially people practicing intermittent fasting may experience[2] irritation, anxiety, etc.

    Whoever practices intermittent fasting reduces calorie intake by a considerable margin.

    The reduced food consumption may lead to low blood sugar levels, making you feel irritated.

    Moreover, the lower blood glucose level may affect concentration and cause anxiety in some people.

    Intermittent fasting practice instantly restricts the consumption of high-calorie or junk food that may lead to irritation or frustration during the initial stage.

  9. May Cause Bad Breath

    Some people have reported experiencing bad breath while doing intermittent fasting.

    But, it is surprising to know that intermittent fasting may cause bad breath in the practitioners.

    During intermittent fasting, the body breaks down fat to get energy for the metabolism and releases acetone as the byproduct.

    The continuous release of acetone leads to the accumulation of acetone in blood and breath, which may cause bad breath.

    Intermittent fasting may also create a water deficit in the body, which causes a dry mouth due to a lack of saliva flow.

    Hence, mouth-drying could be another reason to experience bad breath.

  10. May Experience Sleep Disturbances

    It is believed that people doing intermittent fasting may suffer from sleep disturbance, i.e., lack of sleep or staying asleep for long.

    People who do fasting may boost growth hormones in the body that activate cell growth. Hence, you start feeling active and energetic, which may lead to less sleep.

    Moreover, fasting is linked to enhanced insulin production that may increase the orexin production in the body, hence, you feel more energized and get less sleep.

    People who have their eating hours or meal at night in intermittent fasting may get enough sleep as their stomach is full.

    But, people who have eating hours during the day may not get sufficient sleep due to hunger and craving at night during the initial days.

What Is Intermittent Fasting?

Intermittent fasting is a famous practice of people looking to change their weight, nutrient intake, and lifestyle.

People follow an eating pattern[3] that oscillates between fasting and the eating period in intermittent fasting.

An individual must follow all the fasting rules and restrictions to get the desired results.

Generally, most of the population prefers to follow the 16-hour intermittent fasting. But, some people also consider doing 24-hour fasting twice per week.

In the 16-hour fast, you get an 8-hour window to eat in which you should consume enough calories.

For the remaining 16 hours, you aren’t allowed to consume extra calories except for water and zero-calorie beverages.

But, in the 24-hour fast, you have to fast for at least two days a week for 24 hours.

It will help if you do not consume any calories during the fasting days except for water, while during the non-fasting days, you could consume a diet that may include several healthy snacks for snack time and a balanced diet to fulfill the body’s needs.

Intermittent fasting might be an effective way to get the desired results, but it may have a few negative impacts or side effects on the practitioner.


Intermittent fasting is a great habit to acquire to burn additional fat in the body.

Moreover, intermittent fasting helps you shape your lifestyle and practices that may help you lead a healthy and fit life.

Alongside numerous benefits, there are a few side effects of intermittent fasting.

But, most of the side effects are due to changes in eating habits and may not last for long.

If the side effects persist, consult any dietitian or specialist to get the best advice.


Working4Health prefers using primary and verified references. We have strict sourcing guidelines and our primary references include peer-reviewed research, academic, and medical institution studies.

  1. B T Corley, R W Carroll, R M Hall, M Weatherall, A Parry-Strong, J D Krebs. Intermittent fasting in Type 2 diabetes mellitus and the risk of hypoglycaemia: a randomized controlled trial. Diabet Med. 2018 May;35(5):588-594. doi: 10.1111/dme.13595. Epub 2018 Feb 27. Available from: https://pubmed.ncbi.nlm.nih.gov/29405359/.
  2. Ellen Watkins, Lucy Serpell. The Psychological Effects of Short-Term Fasting in Healthy Women. Front Nutr. 2016; 3: 27. Published online 2016 Aug 22. doi: 10.3389/fnut.2016.00027.
  3. Mary-Catherine Stockman, RD, LDN, Dylan Thomas, MD, Jacquelyn Burke, MS, RD, and Caroline M. Apovian, MD. Intermittent Fasting: Is the Wait Worth the Weight? Curr Obes Rep. 2018 Jun; 7(2): 172–185. doi: 10.1007/s13679-018-0308-9.

Leave a Comment

Working For Health

Working4health provides health news and health information which is backed by science.


Working For Health

#7293, 66 W Flagler Street STE 900 , Miami, FL 33130, United States