Fasting isn’t just a wellness trend, it’s a time-tested practice that may hold surprising benefits for your immune system. From ancient healing rituals to modern science, research shows that intermittent fasting can do far more than support weight loss.
By giving your body strategic breaks from constant digestion, fasting potentially allows cellular repair processes to activate, inflammation to decrease, and immune cells to function more efficiently.
In this article, we’ll examine how fasting may naturally strengthen your body’s defenses.
Explore how strategic fasting + the right support (such as our MCT Energy Oil) may strengthen your immune system – and how you can do it safely.
Key Takeaways
- Intermittent fasting can support immune function by influencing immune cell repair, inflammation and gut health.
- Different types of fasting (time-restricted, 5:2, alternate-day) carry varying levels of benefit and risk.
- Using a high-quality MCT oil during a fast may help maintain energy and support immune health while fasting.
- Fasting isn’t suitable for everyone — pregnant or breastfeeding women, people with eating-disorders or advanced diabetes should seek medical advice.
Introduction to Fasting
Fasting, in its many forms, has been practiced for centuries as a means to promote health and longevity. Today, methods like intermittent fasting (IF) and prolonged fasting are gaining scientific attention for their potential wide-ranging health benefits, especially when it comes to supporting the immune system.
Unlike traditional diets, fasting focuses on when you eat rather than what you eat, offering a flexible approach that can fit into many lifestyles.
We're primarily going to talk about intermittent fasting (IF) in this article as that's the type of fasting most people tend to follow for health and weight loss reasons (as opposed to fasting for religious reasons, for example).
There are several different types of intermittent fasting - you may have heard of the 16/8 method, where you fast or don't eat for 16 hours, only eating within an eight-hour window.
Or the 5:2 diet, where you eat normally for five days but drastically restrict calories for the remaining two (non-consecutive) days.
How IF Differs from Calorie Restriction
Calorie restriction - where you carefully measure and reduce your total calorie intake on a daily basis - may offer numerous benefits, such as weight loss and reduced risk of cardiovascular problems, among other things. However, evidence shows that long-term daily calorie restriction is hard to stick to. (1)
In Contrast...
Intermittent fasting doesn't require you to meticulously monitor your calories or energy intake during your eating intervals.
The Immune Potential of Fasting: Summary
We're going to do a deep dive into the potential immune-boosting properties of fasting later in this article, but for now let me tell you that research suggests fasting can do much more than help with weight loss or metabolic health.
It has been shown to influence the way your immune system works, affecting everything from the activity of immune cells like T cells and B cells to the way your body mounts immune responses against threats.
By modulating both innate and adaptive immune responses (the two main parts of the immune system), fasting may help optimize immune function and even offer potential health benefits for those dealing with autoimmune diseases, inflammatory diseases, or metabolic syndrome.
Understanding how fasting impacts immune cells and immune responses is key to unlocking its therapeutic potential.
Whether you’re interested in boosting your body’s defenses, improving metabolic health, or exploring new ways to manage chronic conditions (as always, speak to a doctor first), learning about the science behind fasting and immunity can provide valuable insights for your wellness journey.
Different Types of Intermittent Fasting or Dietary Restriction
There are three primary forms of widely recognised intermittent fasting. They include:
Alternate Day Fasting
This is typically a two-day cycle where you enjoy unrestricted eating for one day followed by a second day with little caloric intake or complete fasting. A modified version of this fasting allows around 500 calories or 25% of base calories on the second day. You are allowed to drink as much calorie-free drinks - such as water, unsweetened tea and coffee - as you want on the second day. (2, 3)
Some people find this type of fasting easier to stick to. However, if you're doing this for weight loss alone, you may want to know that a year long study discovered alternate day fasting is no better than daily calorie restriction for weight loss. That said, studies have shown that it may help you to lose up to 8% of your body weight in two to three months. (4)
Periodic Fasting
Here you combine days of unconstrained eating with days of calorie restriction. The popular 5:2 fast would fall under this. As I mentioned earlier, this is five days of eating what you want with two days of limited calories per week. A modification of this allows 25-30% of baseline calories on the calorie-restricted days.
The 5:2 diet recommends that the fasting days be non-consecutive, but some forms of periodic fasting encourage consecutive days, making it more extreme. Because of this, it may be harder to stick to. (5)
Time Restricted Feeding
This type of fast restricts caloric intake to a window of several hours, typically between four to 12 hours. There are several variations, such as the 16/8 or 14/10 - where you fast for 16 or 14 hours, and eat during the remaining eight or 10 hour window. You may just skip breakfast or dinner; this is technically classed as a variant of time restricted feeding.
Because this version of fasting encourages daytime eating and fasting at night, it may be potentially more effective at regulating circadian rhythms compared to other forms of fasting. (6)
Boost Your Fasting with MCT Energy Oil
Let's get the obvious question out of the way first: can adding a teaspoon of MCT oil to your unsweetened coffee break a fast? Yes, technically anything that contains calories will break a fast BUT MCT Oil is a little bit different. That's because it may actually help you when you are on a restricted diet.
MCTs are rapidly converted into ketones without spiking insulin. Meaning MCT oil may help increase satiety and energy, and may help you stay in ketosis. Fans of MCT oil suggest it can help focus and energy while fasting.
If you want to try MCT oil during your fast, start slow (too much too soon may cause digestive upsets) and remember that you just need enough to tide you over until you break your fast. It is not a meal replacement. One to two tablespoons should be enough.
We recommend Performance Lab MCT Energy Oil made from organic non-GMO coconuts containing only healthy fats C8 and C10, the highest quality MCTs (Medium Chain Triglycerides). Flavor neutral, it's ideal for adding to drinks, shakes, sauces, dressings and soups.
Why Do People Fast? Health Benefits of Intermittent Fasting
There are a great many reasons why people fast. Fasting is an ancient tradition, encouraged by the likes of Hippocrates and the ancient Greeks. It’s also still a part of many religions.
In recent years, however, the popularity of intermittent fasting (IF) has surged due to issues related to diet, obesity, and metabolic disorders.
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As well as its potential for weight loss, clinical trials have shown that intermittent fasting confers protection for metabolic diseases, insulin resistance/ regulation, and more.
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Fasting has also been studied in cancer patients, where it may help protect immune cells during chemotherapy by reducing DNA damage in leukocytes and potentially improving treatment outcomes. (7)
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Studies have concluded that IF may aid obesity, hypertension, and cardiovascular disease risk factors. Trials have also highlighted metabolic disease as a key pathway influenced by fasting, alongside infectious and immune-related pathways. (8, 9)
Study Results...
One study into fruit flies even suggests that prolonged night time fasting could extend a healthy lifespan. Scientists theorise it could one day offer the same to humans, albeit more human research would be needed. (10, 11)
On top of these potential benefits, as mentioned earlier, there is substantial evidence to suggest that intermittent fasting can strengthen the immune system - and that’s what we’re going to talk about in detail today. Fasting for immunity.
Fasting for Immunity
Fasting has been shown to boost immunity via several different mechanisms. Studies show that fasting affects everything from your hormones to your circadian rhythm, your gut microbiota to lipids, inflammation and oxidative stress.
Fasting also activates AMP activated protein kinase, which regulates autophagy (cell breakdown and recycling), energy metabolism, and anti-inflammatory pathways.
Additionally, fasting can reduce reactive oxygen species which can contribute to oxidative stress, thereby decreasing inflammation and supporting immune health. (12)
Let’s take each one in turn…
Intermittent Fasting and Hormones
Several studies examining the impact of intermittent fasting have catalogued hormonal fluctuations in the bloodstream, leptin being particularly noticeable.
Leptin is a hormone released by your body fat or adipose tissue and it's important for regulating hunger and promoting satiety, thus helping to maintain your weight on a longer term basis.
High levels of leptin can result in leptin resistance, where your brain doesn't respond to the hormone as it should, meaning you never feel full and eat more than you need. (13, 14)
Leptin and Fasting...
Studies have noted that certain types of intermittent fasting may reduce leptin levels. Short fasts of less than 12-14 hours, for example, do not significantly influence leptin concentration, but prolonged fasts may do.
IF, Free Fatty Acids and Energy Metabolism
The most obvious reason for intermittent fasting is weight loss and fat reduction - strengthened immunity is a beneficial by-product.
As we fast, blood glucose levels fall, encouraging the body to draw on liver glycogen stores to combat the lack of food. When these stores are exhausted, the body resorts to burning fat for energy instead.
As a result, more fat molecules (called free fatty acids) are released into the blood, and the body starts making ketones - chemicals produced when fat is broken down. This has been confirmed by several studies on intermittent fasting (IF).
Ketones can reduce excessive inflammation, while some immune cells can use ketones for fuel.
This fat-burning and ketone-producing phase can support and balance immune function, reducing harmful inflammation and improving cell repair. Provided you don’t overdo the fasting and deprive the immune system of the energy and nutrients they need to create new immune cells. (15)
Fasting and the Role of Gut Microbiota in Immune Function
The gut microbiota is the microscopic world inside our intestines that plays hosts to trillions of bacteria, viruses, and fungi, both ‘good’ and ‘bad’. It’s a delicate balancing act and you want more of the good bacteria than you do the bad.
The Gut and Our Immune System
The gut can contribute to immune health significantly. That’s because a whopping 70% of our immune cells are located in the gut, and the gut microbiota can influence the function of certain immune cells. Mucosal immune responses are crucial for maintaining gut barrier integrity and defending against pathogens.
Fasting can help by:
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Boosting microbial diversity
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Increasing the amount of beneficial bacteria in the gut microbiota
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Increasing the production of short chain fatty acids (SCFAs) which can help strengthen the gut wall, regulate immune response, and help to reduce inflammation.
While most studies report beneficial results in the gut microbiota as a result of fasting, results may vary based on age, fasting duration and baseline diet. More research is recommended to account for these. (16)
Study Results...
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Time restricted feeding for 25 days among healthy men reshaped gut microbiota, enhanced diversity, and increased beneficial bacteria. (17)
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A 29-day Ramadan regimen enhanced several strands of beneficial gut bacteria. (18)
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8-weeks time restricted feeding over 8 weeks altered the circadian rhythm of gut microbiota in mice. (19)
Fasting and Irritable Bowel Disease (IBD)
Fasting is often of interest to people with inflammatory bowel disease (IBD) because of its ability to influence gut immunity and reduce inflammation. Current evidence suggests it doesn't have a clear positive value to people with IBD and, in some case, it may have a harmful effect. More research is needed. (20)
Fasting and Immune Cells
When you fast, your immune system temporarily changes how it works. Immune cells like lymphocytes and monocytes, which help fight infection, move out of the bloodstream and back into the bone marrow to rest and repair.
This reduction in circulating immune cells leads to decreased systemic inflammation during fasting.
After immune cells move to the bone marrow, the bone marrow protects these immune cells and optimizes immunological memory during fasting (helping the immune system to remember previous encounters with pathogens, speeding up response in the future).
The migration and function of memory T cells and naive B cells (unactivated B lymphocytes) are also influenced by fasting, which impacts immune memory and the body’s ability to respond to future threats.
After refeeding, immune cells return to the blood, and changes in peripheral blood can be observed; blood samples are used to analyze these immune cell dynamics.
Studies show that fasting cycles may even activate certain immune cells that help the body target cancer cells and enhance red blood cells’ ability to defend against infections, including viruses like SARS-CoV-2. (21, 22)
In short, fasting helps rebalance and rejuvenate the immune system by changing where immune cells are stored and how they function, contributing to the maintenance of immunological memory.
In addition, fasting may help to...
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Clear away damaged cells: Fasting has been shown to enhance immune function by promoting the clearance of damaged or dysfunctional immune cells and generating new ones through fasting-induced cell death - a process that can be beneficial for overall health and disease prevention.
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As mentioned above, short term intensive fasting has been shown to enhance the immune function of red blood cells, which can help to improve oxygen delivery and reduce inflammation. (23)
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Intermittent fasting may reduce serum insulin levels, meaning inflammatory molecules (like cytokines) decrease and immune cells can focus on actual threats (like viruses or bacteria), not unnecessary inflammation.
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Fasting can also affect the function of other blood cells, such as natural killer (NK) cells, which play a crucial role in innate immunity.
REMEMBER: Adding a tablespoon of Performance Lab MCT Energy Oil may help your fast to go smoother. Potentially helping you to feel fuller and focus better.
Fasting and Circadian Rhythms
Circadian rhythms refer to your body’s 24 hour clock, which naturally encourages a shorter eating window in the day (daylight hours), with a longer fast overnight. Circadian rhythm fasting may involve eating from 8am to 8pm, with a 12-hour fast overnight, for example.
Disruption of circadian rhythms can lead to insulin resistance, poor sleep, increased cardiovascular risk, diabetes and more. Fasting has been shown to help restore poor circadian rhythm in shift workers.
The innate immune system is also regulated by circadian clocks, and time-restricted feeding can help synchronize these immune responses, potentially reducing inflammatory conditions. (24)
Time restricted feeding (TRF)
Time restricted feeding (TRF) has the ability to help coordinate the circadian clock. Studies show that time of day influences results. One eight-week study of TRF discovered that eating at midday, for example, allowed greater control of glucose, fat and lipid levels and decreased inflammation. In contrast, people who ate in the afternoon or evening lacked this control.
Innate immune cells possess intrinsic circadian clocks that modulate immune responses such as cytokine production, phagocytosis, and cell migration, and these processes are influenced by the timing of food intake. (25, 26)
Current Limitations and Future of Fasting Research
While intermittent fasting and prolonged fasting has become popular for a broad range of potential health benefits, I’d be remiss if I didn’t point out there are limitations to the research done on fasting so far.
For example...
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While preliminary trials or animal trials show significant promise for various benefits, not all results have been recreated in a clinical setting with humans.
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Likewise, research is typically short-term with very few trials examining its effectiveness as a sustainable long term lifestyle.
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And many of the participants in such trials are overweight and middle-aged. Research would be welcomed into a more diverse population.
Dietary intake regulates immune cell dynamics and responses, so understanding the role of nutrition is crucial in fasting studies.
For our particular interests, we’d also welcome more research into which types of fasting can help which specific immune pathways, and what duration and frequency of fasting is necessary to see such immune boosting benefits.
Researchers are also exploring how intermittent fasting interacts with other dietary strategies, such as the fasting-mimicking diet, and how these combinations might further enhance immune health.
Risks of Fasting
Fasting isn't suitable for everyone. It is not recommended for pregnant or breastfeeding women, people with a history of eating disorders, or anyone with advanced diabetes. In fact, if you have any type of diabetes or medical condition please seek medical advice before starting intermittent fasting.
Please also be aware of the dangers of severe or prolonged fasting, which can lead to malnutrition. On the opposite end of the scale, overeating during the refeeding period will make results difficult to maintain. Some people will also find the fasting difficult to maintain.
Take Home Thoughts
Research tells us that fasting can be a powerful tool for improving immune function, as well as weight loss. By following one of the fasting-types above, we may help our bodies reset immune defenses, correct defective circadian rhythms, improve our gut microbiota and more.
While we'd like more research to determine the best type of fasting for specific immune benefits, we do know that it seems mostly beneficial for many people.
And we also know that adding a dash of MCT oil to a fast may help rather than hinder, assuming you choose a quality product. We think Performance Lab MCT Energy Oil is one of the best.
References
- Nowosad, K., & Sujka, M. (2021). Effect of various types of intermittent fasting (IF) on weight loss and improvement of diabetic parameters in humans. Current Nutrition Reports, 10(2), 146–154.
- Petersen, M. C., Gallop, M. R., Flores Ramos, S., Zarrinpar, A., Broussard, J. L., Chondronikola, M., et al. (2022). Complex physiology and clinical implications of time-restricted eating. Physiological Reviews, 102(4), 1991–2034.
- Hofer, S. J., Carmona-Gutierrez, D., Mueller, M. I., & Madeo, F. (2022). The ups and downs of caloric restriction and fasting: From molecular effects to clinical application. EMBO Molecular Medicine, 14(1), e14418.
- Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., et al. (2017). Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Internal Medicine, 177(7), 930–938.
- Stratton, M. T., Albracht-Schulte, K., Harty, P. S., Siedler, M. R., Rodriguez, C., & Tinsley, G. M. (2022). Physiological responses to acute fasting: Implications for intermittent fasting programs. Nutrition Reviews, 80(3), 439–452.
- Hatori, M., Vollmers, C., Zarrinpar, A., DiTacchio, L., Bushong, E. A., Gill, S., et al. (2012). Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet. Cell Metabolism, 15(6), 848–860.
- Buono, R., & Longo, V. D. (2019). When fasting gets tough, the tough immune cells get going—or die. Cell, 178(5), 1038–1040. https://doi.org/10.1016/j.cell.2019.07.052
- Vasim, I., Majeed, C. N., & DeBoer, M. D. (2022). Intermittent fasting and metabolic health. Nutrients, 14(3), 631.
- Ma, R. (2024). A detective story of intermittent fasting effect on immunity. Immunology, 173(2), 227–247.
- Nature. (2021). Evidence that overnight fasting could extend healthy lifespan.
- Ulgherait, M., Midoun, A. M., Park, S. J., et al. (2021). Circadian autophagy drives iTRF-mediated longevity. Nature, 598, 353–358.
- Ma, R. (2024). A detective story of intermittent fasting effect on immunity. Immunology, 173(2), 227–247.
- Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D. H., Dixit, V. D., et al. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine, 42(5), 665–674.
- Kiernan, K., Nichols, A. G., Alwarawrah, Y., & MacIver, N. J. (2023). Effects of T cell leptin signaling on systemic glucose tolerance and T cell responses in obesity. PLOS ONE, 18(6), e0286470.
- Vasim, I., Majeed, C. N., & DeBoer, M. D. (2022). Intermittent fasting and metabolic health. Nutrients, 14(3), 631.
- Ashique, S., Debnath, B., Mojgani, N., Tariq, M., Haider, T., Shorog, E., et al. (2025). Gut microbiota modulation and health benefits of various fasting regimens. Current Research in Biotechnology, 10, 100311.
- Zeb, F., Wu, X., Chen, L., Fatima, S., Haq, I. U., Chen, A., et al. (2020). Effect of time-restricted feeding on metabolic risk and circadian rhythm associated with gut microbiome in healthy males. British Journal of Nutrition, 123(11), 1216–1226.
- Ozkul, C., Yalinay, M., & Karakan, T. (2020). Structural changes in gut microbiome after Ramadan fasting: A pilot study. Beneficial Microbes, 11(3), 227–233.
- Ye, Y., Xu, H., Xie, Z., Wang, L., Sun, Y., Yang, H., et al. (2020). Time-restricted feeding reduces the detrimental effects of a high-fat diet, possibly by modulating the circadian rhythm of hepatic lipid metabolism and gut microbiota. Frontiers in Nutrition, 7, 596285.
- Healthline. (n.d.). Fasting-mimicking diet for easing IBD symptoms.
- Buono, R., & Longo, V. D. (2019). When fasting gets tough, the tough immune cells get going—or die. Cell, 178(5), 1038–1040.
- Fang, Y., Qian, J., Xu, L., et al. (2023). Short-term intensive fasting enhances the immune function of red blood cells in humans. Immunity & Ageing, 20, 44.
- Fang, Y., Qian, J., Xu, L., et al. (2023). Short-term intensive fasting enhances the immune function of red blood cells in humans. Immunity & Ageing, 20, 44.
- Manoogian, E. N. C., Zadourian, A., Lo, H. C., Gutierrez, N. R., Shoghi, A., Rosander, A., et al. (2022). Feasibility of time-restricted eating and impacts on cardiometabolic health in 24-h shift workers: The healthy heroes randomized control trial. Cell Metabolism, 34(10), 1442–1456.e7.
- Carlson, O., Martin, B., Stote, K. S., Golden, E., Maudsley, S., Najjar, S. S., et al. (2007). Impact of reduced meal frequency without caloric restriction on glucose regulation in healthy, normal-weight middle-aged men and women. Metabolism, 56(12), 1729–1734.
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