The Evidence-Based Benefits of Intermittent Fasting
Intermittent fasting (IF) involves fasting for part of the day and eating within a prescribed window of time. There are many different variations of IF, and there are also some surprising benefits.
Here’s what I say in my book, Intuitive Fasting:
“Fasting is about way more than weight loss. In fact, if you think about fasting the way I do, weight loss isn’t even center stage when it comes to fasting’s benefits. In fact, it really doesn’t have to be on stage at all.”
ARTICLE CONTINUES BELOW
Make Your Life a Cleanse
SUBSCRIBER-ONLY GUIDES FOR GUT HEALTH, VIBRANT ENERGY, HEALTHY FOOD & CLEAN ALCOHOL
Get FREE access to these + giveaways, recipes, & discount codes in personal emails from Dr. Will Cole.
Fasting may lead to healthy weight management, but it also causes fundamental shifts in your body’s physiology — such as improvements in glucose regulation, blood pressure, and heart rate.
Human and animal studies explain that fasting enhances health and leads to weight loss in ways that are unrelated to a calorie deficit. IF triggers shifts in metabolic and hormonal pathways that naturally help you maintain a healthy body (including, but not limited to, weight loss).
Let’s talk about IF benefits, looking beyond just weight management and sticking to the evidence.
1. Improved Digestion
Intermittent fasting may improve gut health and digestion by reducing inflammation, as well as strain on your digestive system. Intermittent fasting may even have a positive effect on your gut microbiome. (1)
Many of my patients have irritable bowel syndrome, inflammatory bowel disease, or simple but frequent indigestion. Elimination diets are effective when they are temporary, but so many are constantly trying to find the food group that’s triggering digestive issues.
I often recommend a fasting protocol for digestive issues. Studies have shown that IF lowers gut inflammation and helps improve inflammatory gut disorders such as Crohn’s disease, ulcerative colitis, and IBS. (2)
For more, check out my book, Intuitive Fasting.
2. Better Brain Health
Intermittent fasting may lead to better brain health, possibly due to decreased inflammation and oxidative stress. IF’s antioxidant and anti-inflammatory properties may even increase lifespan by improving brain function, cutting down on brain fog, and reducing your risk of age-related diseases.
I was pleasantly shocked to learn about the strong preclinical evidence that shows how fasting can prevent and slow down the progression of conditions like Parkinson’s and Alzheimer’s disease. (3)
IF increases your brain cells’ ability to resist stress. It also stimulates autophagy, which boosts mitochondrial function, antioxidant defenses, and DNA repair. Fasting also supports neuroplasticity, which is the brain’s ability to reorganize itself and form new neural connections. (4)
3. Better Blood Sugar Control
Intermittent fasting may more effectively regulate your blood sugar levels. People with diabetes and prediabetes may benefit from IF’s impact on insulin resistance, but remember to talk to your healthcare provider before making lifestyle changes to treat diabetic conditions.
The CDC estimates that about half of the US is prediabetic or diabetic. I did not mistype that — 50 percent of Americans have a major blood sugar problem. What’s more, many of these people don’t know they have type 2 diabetes!
When patients come in with blood sugar problems, I like to recommend IF due to its potent ability to improve insulin resistance. (5)
Researchers from the University of Alabama conducted a study on the impact of fasting on obese men with prediabetes. They compared restricting eating to an 8-hour period per day to a 12-hour period. Both groups maintained the same weight after 5 weeks, but the 8-hour eating window group had dramatically lower insulin levels and significantly improved insulin sensitivity. (6)
Read More: What Is Intuitive Eating?
4. Weight Management
Although it’s not the only reason you should fast intermittently, healthy weight management is a huge benefit of fasting therapy. IF may also reduce your risk for the many chronic diseases that come with high body fat. It also reduces snacking!
IF is an efficient dietary plan for people with obesity to achieve weight loss and for everyone to maintain a healthy weight. Some researchers conclude IF is especially effective in the short-term, as in 1 to 3 months. (7)
A recent systematic review found that IF helped overweight and obese people lose 0.8% to 13.0% of their baseline weight. These researchers were optimistic, but they encouraged future researchers to engage in more long-term studies into IF’s impact on obesity and weight. (8)
There are so many benefits to intermittent fasting besides weight loss, but managing a healthy weight is indeed an IF benefit.
5. Improved Mental Health
Intermittent fasting often directly and indirectly influences mental health and mood disorders like depression. Fasting endorphins are mood-enhancing hormones that IF may release.
A 2023 review concluded that IF benefits mood through the following mechanisms: (9)
- Better metabolism
- Favorable body composition
- Improved gut bacteria balance
- Healthy circadian rhythm
- Neurogenesis
- Increased availability of neurotransmitters
IF has shown a lot of promise in improving stress, anxiety, and depression symptoms, especially when there is some measure of caloric restriction. Multiple reviews have found that IF is safe even for people with diabetes. (10)
Improved mental health is a benefit I hear from my patients and social media followers all the time — I’ve even experienced this benefit in my own life!
@drwillcole intuitive fasting is out now (drwillcole.com) #health #wellness #intermittentfasting #selfcare #intuitiveeating #mindfulness #selfcareroutine ♬ Ocean - Martin Garrix,Khalid
6. Sustained Energy Levels
Intermittent fasting can put your body into ketosis, which means you start burning ketones for fuel instead of sugar (AKA glucose, which is a carbohydrate). Ketones are a more efficient fuel than glucose. This means you should have more sustained energy levels throughout the day when you intermittent fast.
Ketosis has been shown to increase mitochondria biogenesis, which just means the making of new mitochondria. (11)
If you’ve never heard of the mitochondria before, they’re known as the “energy centers” of your cells. They are what allow us to turn the nutrients we eat into a specific form of energy (called ATP) that fuels our body. The healthier our mitochondria, the better energy levels we have.
Are you a hangry sugar-burner or an energetic fat-burner? Let's find out.
7. Better Heart Health
You may experience better heart health when you do intermittent fasting.
Heart disease is the #1 cause of death worldwide and impacts millions of people every day. I often tell my patients that several cardiovascular diseases can be prevented with a healthy lifestyle, proper nutrition, regular exercise, stress reduction, and, yes — intermittent fasting!
The evidence is clear. Fasting benefits the cardiovascular system, especially when it comes to risk factors such as unhealthy cholesterol markers, high blood pressure, and unhealthy levels of triglycerides. (12)
A review of human and animal studies showed that intermittent fasting led to higher levels of “good” cholesterol (called HDL cholesterol) and lower levels of inflammatory “bad” cholesterol particles (called LDL cholesterol). (13)
8. Improved Immune System Function
Fasting is a great way to safeguard your metabolism, but it’s also a great way to support the health of the rest of your body, including your immune system. Studies have shown (14) that intermittent fasting can upregulate proteins that protect us from obesity, diabetes, and metabolic problems, Alzheimer’s disease, and neuropsychiatric disorders. It can also induce proteins that protect our DNA, prevent cancer, and support our immune systems.
Another study (15) that tested fasting in mice and humans showed that fasting lowered white blood cell counts, which triggered the species’ immune system to produce new white blood cells, which are a critical part of the immune system. In both species, fasting lowered white blood cell counts, which in turn triggered the immune system to start producing new white blood cells. White blood cells (or lymphocytes) are a key component of your body’s immune system. According to the researchers who conducted that study, fasting can trigger the body to recycle immune cells that are not needed.
9. Increased Efficacy Of Chemotherapy
I’ll end with the incredible emerging benefits of fasting during chemotherapy treatment.
Short-term fasting during chemotherapy treatment increases the efficacy of chemotherapy and reduces its many side effects, according to recent research. (16)
Below are the different ways that scientists believe fasting may help reduce the side effects and increase the effectiveness of chemotherapy:
- Increased stress resistance of healthy cells
- Shortage of nutrients (including glucose) which tumor cells feed on
- Decreased tumor cell resistance to chemotherapeutic agents
- Reduction in fatigue after chemotherapy
- Higher quality of life (17)
Bonus: Intermittent Fasting Simplifies Your Life
Intermittent fasting is a great practice not only because it’s good for your body, but it also simplifies your life - a lot. Instead of keeping track of how much you’ve eaten or even what you’ve eaten (as long as we're talking about healthy, whole foods!), the only question you really need to ask yourself is: “Am I inside or outside my eating window?” If you’re inside your eating window, go ahead and enjoy that snack with zero regrets. If your eating window is over or hasn’t yet begun for the day, put down that snack and make yourself a cup of herbal tea instead. Simple as that.
This simplicity is incredibly liberating. As an added bonus, intermittent fasting also means less time in the kitchen. I don’t know about you, but I’m getting a little tired of the “cook, eat, clean” routine. When you limit yourself to an eating window, you get to prep, prepare, and clean up from fewer meals every day. Win-win!
Try The Fasting Schedule That Works For You
There are different fasting schedules you can try out. Choose the fasting and eating pattern that works for your overall health conditions, family life, work schedule, etc. We all have bioindividuality — all of us respond positively to different plans.
Here are the most common intermittent fasting schedules:
- The 16:8 diet means 16 hours of fasting and 8 hours of healthy eating, typically between 12:00 PM and 8:00 PM.
- The 14:10 diet means 14 hours of fasting and 10 hours of healthy eating, typically between 10:00 AM and 8:00 PM.
- The 12:12 diet, also called overnight fasting, means 12 hours of fasting and 12 hours of eating, typically between 8:00 AM and 8:00 PM. This IF schedule is a good way to ease into intermittent fasting because the eating window is already similar to when many people eat.
- The 5:2 method means you eat normally for 5 days out of the week but, on the 2nd and 5th day of the week, restrict your calorie intake to 20-25% of your average daily intake (500-600 calories).
- Alternate-day fasting means you eat normally every other day while fasting or adhering to a severe calorie restriction on the in-between days.
- The Warrior Diet, also called the 20:4 diet, means you only eat certain fruits and vegetables (partial fast) until a 4-hour window when you can consume the remaining calories in your daily allowance. This is not for beginners — I would only recommend this to experienced fasters, as the fasting period is incredibly long, and 4 hours is a very short time to get a full day of calories in.
16 hours is sort of the magic number for fasting — as in, it’s the most common period of time people intermittently fast to maintain a healthy body weight, among other benefits.
READ NEXT: Intimidated by Fasting? Here’s What an 18-Hour Fast Looks Like
Intermittent Fasting Isn’t Right For Everyone
Fasting is not just about weight loss. Intermittent fasting can improve your digestion, brain health, heart health, and more. IF is about longevity, energy, and happiness — not just restriction. In fact, I see intermittent fasting as a way to break free of diet culture and show yourself some love.
Still, IF comes with pros and cons. There are people who shouldn’t try intermittent fasting, including:
- People with a history of eating disorders
- People with type 1 diabetes
- People trying to build a lot of muscle mass
- Children under 18 years old
- People who are pregnant or breastfeeding
If you want to try fasting for its potential benefits for a specific condition, make sure to consult with your primary care provider or prescribing physician to understand how these changes may interfere with your treatments or medications. 12:12 fasting and other gentle fasting methods are unlikely to create issues, but a very restrictive schedule might.
As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people from around the globe. Learn how you can become a patient today!
READ NEXT: Are Fat Burners Safe? Ingredients To Look For And What To Avoid
Start Your Health Journey Today
FUNCTIONAL MEDICINE CONSULTATIONS FOR PEOPLE AROUND THE WORLD
- Paukkonen, I., Törrönen, E. N., Lok, J., Schwab, U., & El-Nezami, H. (2024). The impact of intermittent fasting on gut microbiota: a systematic review of human studies. Frontiers in Nutrition, 11, 1342787.
- Moro, T., Tinsley, G., Pacelli, F. Q., Marcolin, G., Bianco, A., & Paoli, A. (2021). Twelve months of time-restricted eating and resistance training improves inflammatory markers and cardiometabolic risk factors. Medicine and science in sports and exercise, 53(12), 2577.
- Roco-Videla, Á., Villota-Arcos, C., Pino-Astorga, C., Mendoza-Puga, D., Bittner-Ortega, M., & Corbeaux-Ascui, T. (2023). Intermittent Fasting and Reduction of Inflammatory Response in a Patient with Ulcerative Colitis. Medicina, 59(8), 1453.
- Elias, A., Padinjakara, N., & Lautenschlager, N. T. (2023). Effects of intermittent fasting on cognitive health and Alzheimer’s disease. Nutrition Reviews, 81(9), 1225-1233.
- Mattson, M. P., Moehl, K., Ghena, N., Schmaedick, M., & Cheng, A. (2018). Intermittent metabolic switching, neuroplasticity and brain health. Nature Reviews Neuroscience, 19(2), 81-94.
- Yuan, X., Wang, J., Yang, S., Gao, M., Cao, L., Li, X., ... & Sun, C. (2022). Effect of intermittent fasting diet on glucose and lipid metabolism and insulin resistance in patients with impaired glucose and lipid metabolism: a systematic review and meta-analysis. International journal of endocrinology, 2022.
- Jamshed, H., Beyl, R. A., Della Manna, D. L., Yang, E. S., Ravussin, E., & Peterson, C. M. (2019). Early time-restricted feeding improves 24-hour glucose levels and affects markers of the circadian clock, aging, and autophagy in humans. Nutrients, 11(6), 1234.
- Shalabi, H., Hassan IV, A. S., Al-Zahrani, F. A., Alarbeidi, A. H., Mesawa, M., Rizk, H., ... & Aljubayri IV, A. A. (2023). Intermittent Fasting: Benefits, Side Effects, Quality of Life, and Knowledge of the Saudi Population. Cureus, 15(2).
- Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (2020). Intermittent fasting and weight loss: Systematic review. Canadian Family Physician, 66(2), 117-125.
- Murta, L., Seixas, D., Harada, L., Damiano, R. F., & Zanetti, M. (2023). Intermittent Fasting as a Potential Therapeutic Instrument for Major Depression Disorder: A Systematic Review of Clinical and Preclinical Studies. International Journal of Molecular Sciences, 24(21), 15551.
- Berthelot, E., Etchecopar-Etchart, D., Thellier, D., Lancon, C., Boyer, L., & Fond, G. (2021). Fasting interventions for stress, anxiety and depressive symptoms: a systematic review and meta-analysis. Nutrients, 13(11), 3947.
- Hasan-Olive, M. M., Lauritzen, K. H., Ali, M., Rasmussen, L. J., Storm-Mathisen, J., & Bergersen, L. H. (2019). A ketogenic diet improves mitochondrial biogenesis and bioenergetics via the PGC1α-SIRT3-UCP2 axis. Neurochemical research, 44, 22-37.
- Hailu, K. T., Salib, K., Nandeesha, S. S., Kasagga, A., Hawrami, C., Ricci, E., & Hamid, P. (2024). The Effect of Fasting on Cardiovascular Diseases: A Systematic Review. Cureus, 16(1).
- Mindikoglu, Ayse L., Mustafa M. Abdulsada, Antrix Jain, Jong Min Choi, Prasun K. Jalal, Sridevi Devaraj, Melissa P. Mezzari, Joseph F. Petrosino, Antone R. Opekun, and Sung Yun Jung. “Intermittent Fasting from Dawn to Sunset for 30 Consecutive Days Is Associated with Anticancer Proteomic Signature and Upregulates Key Regulatory Proteins of Glucose and Lipid Metabolism, Circadian Clock, DNA Repair, Cytoskeleton Remodeling, Immune System and Cognitive Function in Healthy Subjects.” Journal of Proteomics 217 (April 15, 2020): 103645. https://doi.org/10.1016/j.jprot.2020.103645.
- Cheng, C. W., Adams, G. B., Perin, L., Wei, M., Zhou, X., Lam, B. S., Da Sacco, S., Mirisola, M., Quinn, D. I., Dorff, T. B., Kopchick, J. J., & Longo, V. D. (2014). Prolonged fasting reduces IGF-1/PKA to promote hematopoietic-stem-cell-based regeneration and reverse immunosuppression. Cell stem cell, 14(6), 810–823. https://doi.org/10.1016/j.stem.2014.04.014
- Rothschild, J., Hoddy, K. K., Jambazian, P., & Varady, K. A. (2014). Time-restricted feeding and risk of metabolic disease: a review of human and animal studies. Nutrition reviews, 72(5), 308-318.
- de Groot, S., Pijl, H., van der Hoeven, J. J., & Kroep, J. R. (2019). Effects of short-term fasting on cancer treatment. Journal of Experimental & Clinical Cancer Research, 38, 1-14.
- Schmidt, M. W., Brenner, W., Gebhard, S., Schmidt, M., Singer, S., Weidenbach, L., ... & Anic, K. (2023). Effects of intermittent fasting on quality of life tolerance of chemotherapy in patients with gynecological cancers: Study protocol of a randomized-controlled multi-center trial. Frontiers in Oncology, 13.
The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.
Our content may include products that have been independently chosen and recommended by Dr. Will Cole and our editors. If you purchase something mentioned in this article, we may earn a small commission.
BY DR. WILL COLE
Dr. Will Cole, DNM, IFMCP, DC is a leading functional medicine expert who consults people around the globe, starting one of the first functional medicine telehealth centers in the world. Named one of the top 50 functional and integrative doctors in the nation, Dr. Will Cole provides a functional medicine approach for thyroid issues, autoimmune conditions, hormonal imbalances, digestive disorders, and brain problems. He is also the host of the popular The Art of Being Well podcast and the New York Times bestselling author of Intuitive Fasting, Ketotarian, Gut Feelings, and The Inflammation Spectrum.
Gut Feelings
Healing The Shame-Fueled Relationship
Between What You Eat And How You Feel