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Is Intermittent Fasting Healthy?

Intermittent fasting is a popular method for weight loss and improvement of overall health. Read on to learn why intermittent fasting is healthy.
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Many people are interested in trying intermittent fasting to lose some weight and regain control of their health. Before starting intermittent fasting, it is important to understand the benefits and drawbacks of the diet in order to make an informed decision.

Written by
Christine Richardson, PhD
Clinical Project Manager at Becton Dickinson

It seems like everyone is trying out some version of intermittent fasting and you may be wondering if intermittent fasting is actually healthy. The short answer is yes. In fact, there are many studies that show how this dietary pattern can improve various aspects of your health.

In this article, we’re going to discuss some of the pros and cons associated with intermittent fasting.


1. Fat Loss

Woman with a measuring tape.

There’s a reason why we didn’t say “weight loss” and instead chose “fat loss.” That’s because the two are very different. Weight loss can mean a loss in muscle or bodily fluid; whereas fat loss is exactly what it sounds - a loss in body fat. Losing body fat and maintaining muscle mass should be the goal of any “weight loss” diet and intermittent fasting does exactly that.

An excellent review was published claiming that fasting helps to “train” your body to use more fat for energy instead of your stored sugar (1). This means that you can burn more fat no matter what you’re doing! 

Studies also show that intermittent fasting doesn’t affect how many calories you burn each day (2,3). This means that you’re less likely to experience a “plateau” like you would with restricting calories.

2. Autophagy

Autophagy occurs when the body goes without food, meaning this occurs in people who are intermittent fasting. Autophagy is when your body breaks down old cells and recycles them in order to make new ones. It is thought that this process developed as a stress response to protect our ancestors against famine. 

Benefits of autophagy include a decreased risk of cardiovascular disease, decreased inflammation, decreased risk of neurodegenerative disorders such as Parkinson’s disease or Alzheimer’s disease, and it can slow down the aging process(4,5).

3. Insulin Resistance

Type 2 diabetes is extremely common in developed countries. What happens is that your body isn’t as sensitive to insulin so sugar stays in the blood longer, which can have some damaging effects. 

Intermittent fasting has been shown to reduce blood sugar levels and improve insulin resistance in both animal and human studies(6,7). In fact, a case study that involved 3 diabetic subjects found that intermittent fasting was so effective, the individuals didn’t need to continue with insulin therapy(8). 

However, if you have type 2 diabetes, please don’t try fasting or stop your insulin therapy without talking to your physician first; more studies are needed on this topic to show if fasting is an effective medical treatment for this disease.

What these studies do show is promise and how intermittent fasting can be used by non-diabetics as a means of decreasing their risk of ever getting type 2 diabetes.

4. Cardiovascular disease

Model of a heart.

Cardiovascular disease is another disease that is very common in developed countries and is one of the leading causes of deaths (9).

Intermittent fasting has been shown to decrease hypertension (blood pressure) decrease total and LDL cholesterol (7,10).

More studies are needed to show if intermittent fasting can decrease the risk of cardiac events like stroke and heart attack but it appears that fasting decreases some of the risk factors associated with these episodes.

5. Inflammation

“Inflammation” and “anti-inflammatory” are 2 common words you hear but what does this actually mean? Inflammation, despite having a bad reputation, is actually a defense mechanism and is how your body protects and heals itself. Inflammation is actually defined as the activation of immune cells that protect you from bacteria, viruses, toxins, and bodily injury. 

However, when this immune response is chronic, it can cause a variety of conditions such as asthma, cancer, damage to internal organs, and metabolic diseases (11). What often causes chronic inflammation is bad dietary habits, being overweight, not exercising, and more.

Several studies have shown the anti-inflammatory effects of intermittent fasting, meaning this diet may be a useful tool for preventing chronic inflammation and the health risks associated with it (2,12,13). 

6. Gut Health

Woman with a hand on her belly.

Optimizing your gut health by changing the type and amount of your gut microbes or “gut bugs” is definitely a diet trend right now. Probiotic and prebiotic supplements are everywhere…and they’re expensive. But you don’t need to waste your money on fancy supplements to optimize your gut can just fast!

First, let’s talk about why gut health is important. While scientists have so much more to learn about the microbes in our gut and how they influence our health, it has become obvious that having a healthy gut is key for improving and optimizing our overall health.

Like we mentioned, scientists have a lot to learn about our gut microbiome so there aren’t many studies on how intermittent fasting can affect your gut bugs. But it does appear that fasting can help remodel the gut microbiome, leading to an improvement in overall health (14,15).

7. Cancer

Cancer is another disease that plagues many individuals. It’s a terrible illness and the treatment for many cancers isn’t guaranteed…or there simply isn’t one at all. 

Cancer is a group of diseases where, to keep things simple, a few cells are created with a unique mutation. These cells are able to grow rapidly and spread their mutation to other cells, thereby infecting other parts of the body. 

While we still have a lot to learn about the mechanisms involved, it appears that there are a few ways intermittent fasting can help decrease the risk of cancer including hormonal changes, increased autophagy, decreased oxidative stress, and more (16). Additionally, many studies have shown how fasting can enhance cancer treatment for individuals undergoing chemotherapy (17).

8. Increased Lifespan

Yes, you read that right. Intermittent fasting may help increase your lifespan. 

Unfortunately, there are no human studies on this subject but some studies have shown an up to 80% increase in lifespan in animals who fasted when compared to animals that ate daily (18). 

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1. Dehydration

Intermittent fasting helps to “teach” your body to use more of your stored fat for energy as opposed to carbohydrates. Before this happens, your body is going to tap into its stored carbohydrates for energy.

This process causes your body to lose more water and salt in urine, meaning if you are not compensating by drinking more, you may become dehydrated. 

To make sure you are properly hydrated, monitor the color of your urine. It should be clear to a pale-yellow color. If your urine is a dark yellow or orange color, you are most likely dehydrated and should drink some water.

2. Not Eating Enough

With intermittent fasting, you are consuming fewer meals….duh. However, you don’t want this to translate into a large calorie deficit every day. 

We eat food to fuel our bodies so you want to make sure you are giving your body what it needs. 

This may seem counterintuitive to what we’ve all been taught because eating less calories should lead to weight loss right? Yes and no. You might lose some weight initially but your body will likely adapt and burn less calories overall each day; this is why people tend to plateau when restricting calories. 

Restricting too many calories can also lead to feelings of fatigue and grumpiness. 

Try logging your food to see how many calories you are eating relative to how much you need each day. If you are in a major calorie deficit (500+ calories each day), look for ways to incorporate more calorie-dense food items.

3. Malnutrition

This risk is very similar to not eating enough calories. If you are not eating enough food, there is a good chance you are not consuming enough nutrients like vitamins and minerals.

Again, make sure you are eating enough nutrient-dense and calorie-dense food in order to reach your calorie and nutrient recommendations.

4. Problems Sleeping

Woman sleeping in bed.

Interestingly, some people who try intermittent fasting report having problems with sleeping. Specifically, individuals claim that they have trouble falling asleep and will often wake up multiple times in the middle of the night.

There have been a couple studies that investigated this side effect and reported opposite conclusions(19,20). 

If you try fasting and have trouble sleeping, give it a few days to see if your body is just adjusting. If this problem persists, fasting may not be the right diet for you.

5. Weight Gain

Weight gain? Intermittent fasting is supposed to help with weight loss right? Yes, it can likely help with weight loss but only if done correctly. 

Many people hear that with fasting, you can skip a meal or meals and then eat whatever you want. This is NOT true. If you decide to eat very calorie-dense meals only, then you can still eat more calories than you burn each day. This will cause weight gain.

Some people also get very hungry at night and binge while intermittent fasting, which could be a result of these individuals not eating enough during the day. Late night binging is another cause of weight gain(21).

To combat these, make sure you are eating a balanced diet. Eat nutrient dense food throughout the day and make sure you are getting enough calories. If you feel incredibly hungry at night, try eating more during the day. 

In Summary

Intermittent fasting is a healthy dietary pattern that may improve your quality of life. By making intermittent fasting a habit, you can reduce your risk of many diseases, lose body fat, and maybe even live longer!

Read more and find out if intermittent fasting is good for you here.


1. Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous AG, Leeuwenburgh C, Mattson MP. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity. Blackwell Publishing Inc.; 2018. p. 254–68. 

2. Moro T, Tinsley G, Bianco A, Marcolin G, Pacelli QF, Battaglia G, Palma A, Gentil P, Neri M, Paoli A. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med [Internet]. BioMed Central; 2016 [cited 2018 Mar 6];14:290. Available from:

3. Tinsley GM, Moore ML, Graybeal AJ, Paoli A, Kim Y, Gonzales JU, Harry JR, Vandusseldorp TA, Kennedy DN, Cruz MR. Time-restricted feeding plus resistance training in active females: a randomized trial. Am J Clin Nutr [Internet]. 2019 [cited 2020 May 21];110:628–40. Available from: https://academic.oup.c

4. Martinez-Lopez N, Tarabra E, Toledo M, Garcia-Macia M, Sahu S, Coletto L, Batista-Gonzalez A, Barzilai N, Pessin JE, Schwartz GJ, et al. System-wide Benefits of Intermeal Fasting by Autophagy. Cell Metab [Internet]. Cell Press; 2017 [cited 2021 Jun 9];26:856-871.e5. Available from: /pmc/articles/PMC5718973/

5. Fujikake N, Shin M, Shimizu S. Association between autophagy and neurodegenerative diseases [Internet]. Frontiers in Neuroscience. Frontiers Media S.A.; 2018 [cited 2021 Jun 9]. p. 255. Available from: /pmc/articles/PMC5972210/

6. Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab. Cell Press; 2018;27:1212-1221.e3. 

7. Mattson MP, Longo VD, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Research Reviews. Elsevier Ireland Ltd; 2017. p. 46–58. 

8. Furmli S, Elmasry R, Ramos M, Fung J. Therapeutic use of intermittent fasting for people with type 2 diabetes as an alternative to insulin. BMJ Case Rep [Internet]. BMJ Publishing Group; 2018 [cited 2021 May 18];2018. Available from: /pmc/articles/PMC6194375/

9. Organization WH. Cardiovascular diseases (CVDs) [Internet]. [cited 2020 May 21]. Available from:

10. Malinowski B, Zalewska K, Węsierska A, Sokołowska MM, Socha M, Liczner G, Pawlak-Osińska K, Wiciński M. Intermittent fasting in cardiovascular disorders—an overview. Nutrients. MDPI AG; 2019. 

11. Furman D, Campisi J, Verdin E, Carrera-Bastos P, Targ S, Franceschi C, Ferrucci L, Gilroy DW, Fasano A, Miller GW, et al. Chronic inflammation in the etiology of disease across the life span. Nat Med [Internet]. Nature Research; 2019 [cited 2021 Jun 9];25:1822–32. Available from: /pmc/articles/PMC7147972/

12. Adda L, Melhem SA, Pol J. Fasting reduces inflammation associated with chronic inflammatory diseases without affecting the immune response to acute infections. Medecine/Sciences [Internet]. Editions EDK; 2020 [cited 2021 Jun 9];36:665–8. Available from:

13. Longo VD, Mattson MP. Fasting: Molecular mechanisms and clinical applications. Cell Metabolism. NIH Public Access; 2014. p. 181–92. 

14. Maifeld A, Bartolomaeus H, Löber U, Avery EG, Steckhan N, Markó L, Wilck N, Hamad I, Šušnjar U, Mähler A, et al. Fasting alters the gut microbiome reducing blood pressure and body weight in metabolic syndrome patients. Nat Commun [Internet]. Nature Research; 2021 [cited 2021 May 24];12:1–20. Available from:

15. Stockman MC, Thomas D, Burke J, Apovian CM. Intermittent Fasting: Is the Wait Worth the Weight? Current obesity reports. NIH Public Access; 2018. p. 172–85. 

16. Deligiorgi M V., Liapi C, Trafalis DT. How far are we from prescribing fasting as anticancer medicine? [Internet]. International Journal of Molecular Sciences. MDPI AG; 2020 [cited 2021 Jun 9]. p. 1–30. Available from: /pmc/articles/PMC7730661/

17. Zhang J, Deng Y, Khoo BL. Fasting to enhance Cancer treatment in models: The next steps [Internet]. Journal of Biomedical Science. BioMed Central Ltd.; 2020 [cited 2021 Jun 9]. Available from: /pmc/articles/PMC7201989/

18. Goodrick CL, Ingram DK, Reynolds MA, Freeman JR, Cider NL. Effects on intermittent feeding upon growth and life span in rats. Gerontology [Internet]. Gerontology; 1982 [cited 2021 Jun 2];28:233–41. Available from:

19. Cienfuegos S, Gabel K, Kalam F, Ezpeleta M, Pavlou V, Lin S, Wiseman E, Varady KA. The effect of 4-h versus 6-h time restricted feeding on sleep quality, duration, insomnia severity and obstructive sleep apnea in adults with obesity. Nutr Health [Internet]. SAGE Publications Ltd; 2021 [cited 2021 Jun 19]; Available from:

20. De Toledo FW, Grundler F, Bergouignan A, Drinda S, Michalsen A. Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects. PLoS One [Internet]. Public Library of Science; 2019 [cited 2021 Jun 19];14. Available from: /pmc/articles/PMC6314618/

21. Yoshida J, Eguchi E, Nagaoka K, Ito T, Ogino K. Association of night eating habits with metabolic syndrome and its components: A longitudinal study. BMC Public Health [Internet]. BioMed Central Ltd.; 2018 [cited 2021 Jun 19];18. Available from: /pmc/articles/PMC6288903/

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