11 Health Benefits of Fasting: What the Research Shows

Updated October 2026: refreshed the research behind each benefit with current trials and meta-analyses, corrected claims the evidence no longer supports, added safety considerations for practitioners and replaced consumer sign-up links.

Fasting vs. Starvation

Many people mistake the practice of fasting for starvation, especially in the United States, where food is abundant and being hungry is perceived as a negative state (or altogether inhumane, something only happening to the "less fortunate"). The truth is, fasting and starvation are two completely different things. That's why we put together this list of 11 remarkable health benefits of fasting, but before we dive in, a few background points.

Starvation deprives the body of nutrition over a long period and begins the process of breaking it down. Fasting, on the other hand, is a planned, time-limited and controlled practice. Used appropriately, it can support weight management, metabolic health and other markers of healthy aging. That's why we've compiled this list of the benefits of fasting, the healthy way, as recommended by Dr. John Limansky, the Keto Doctor, Heads Up friend and advisor. Thank you, Dr. John!

Much of the research below covers intermittent fasting approaches such as time-restricted eating (TRE), alternate-day fasting and the 5:2 diet, as well as some studies of longer fasts. Results differ between these approaches, so we note where the evidence is strong and where it is still early.

The Health Benefits of Fasting

Achieve a healthier weight. Fasting is one way to reduce overall energy intake, and during longer fasting periods the body burns through its glycogen stores and then shifts toward burning fat, a process known as metabolic switching (de Cabo and Mattson, 2019). A 2025 network meta-analysis of 99 randomized trials found that all intermittent fasting strategies reduced body weight compared with unrestricted eating, with alternate-day fasting showing a modest advantage over daily calorie restriction (Semnani-Azad et al., 2025). In a 12-month trial, time-restricted eating combined with calorie restriction was not significantly better than calorie restriction alone (Liu et al., 2022). For many clients, fasting works because it is a sustainable way to eat less, not because it is uniquely powerful.
Improve insulin sensitivity and blood sugar control. Fasting gives cells a break from constant insulin exposure. In a supervised crossover trial in men with prediabetes, five weeks of early time-restricted feeding (a 6-hour eating window with dinner before 3 p.m.) improved insulin sensitivity, beta-cell responsiveness and blood pressure, even without weight loss (Sutton et al., 2018). Meta-analyses of randomized trials also report reductions in fasting glucose, fasting insulin and HOMA-IR (Patikorn et al., 2021). Whether this translates into a lower long-term risk of type 2 diabetes has not yet been shown in long-term trials.
Temporarily increase resting metabolism. It's long been believed that fasting brings your metabolism to a grinding halt. In the short term, the opposite can happen: in a small study of 11 lean adults, resting energy expenditure rose by about 14% by day 3 of an 84-hour fast. This was accompanied by a rise in norepinephrine, a stress hormone that helps release fatty acids from fat cells so the body can use its fat stores for fuel (Zauner et al., 2000). This is a short-term effect from a small study and should not be read as a long-term boost to metabolic rate.
Activate adaptive stress responses. Fasting is a mild, intermittent stressor, and cells respond by strengthening their defenses, including antioxidant defenses, DNA repair, protein quality control and mitochondrial function (de Cabo and Mattson, 2019). The effect on cortisol itself is less clear than once claimed: studies are inconsistent, and a meta-analysis of Ramadan fasting in healthy adults found no statistically significant change in morning cortisol (Poursalehian et al., 2024). Tracking sleep and heart rate variability is a practical way to see how each client is handling the added stress of a fasting protocol.
Lower markers of inflammation. Inflammation occurs in response to injury and disease, and in some cases the immune system continues releasing inflammatory chemicals after the original trigger is gone, which can contribute to chronic disease. A 2025 meta-analysis of 21 studies found that intermittent fasting reduced TNF-alpha, C-reactive protein (CRP) and leptin compared with controls, although it did not significantly change IL-6 (Khalafi et al., 2025). In mechanistic research, short-term fasting reduced the number and inflammatory activity of circulating monocytes without compromising the response to acute infection (Jordan et al., 2019).
Support immune regeneration. In mice, repeated cycles of prolonged fasting lowered IGF-1 and PKA signaling, which promoted the self-renewal of blood-forming stem cells and the regeneration of immune cells, and reversed chemotherapy-related immune suppression. Preliminary data in patients who fasted around chemotherapy suggested similar protection of lymphocytes (Cheng et al., 2014). This is promising, but human evidence is still limited, and the idea of "regenerating a whole new immune system" goes beyond what has been shown.
Improve cardiovascular risk factors. Meta-analyses of randomized trials report modest reductions in blood pressure, LDL cholesterol, total cholesterol and triglycerides with intermittent fasting, although most of this evidence is of low to moderate quality and comes from short trials (Patikorn et al., 2021). Lipid responses also vary by approach: in the 2025 network meta-analysis, time-restricted eating produced a small increase in LDL cholesterol compared with whole-day fasting (Semnani-Azad et al., 2025). Long-term data on heart attacks and strokes are still lacking.
Support brain health. In animal studies, intermittent fasting increases production of brain-derived neurotrophic factor (BDNF), stimulates the growth of new neurons, improves learning and memory, and makes neurons more resistant to injury and neurodegenerative disease (Mattson et al., 2018). Most of this evidence comes from animal research, and human trials on cognition, mood and dementia risk remain small and early.
A possible role in cancer care. Cancer is characterized by the rapid and uncontrolled growth of cells, and growth signals such as insulin-like growth factor 1 (IGF-1) play a role. Prolonged fasting lowers circulating IGF-1 (Cheng et al., 2014). In a randomized phase 2 trial in 131 women with HER2-negative breast cancer, a fasting-mimicking diet around chemotherapy did not increase toxicity and was associated with better radiological and pathological responses (de Groot et al., 2020). Fasting has not been shown to prevent cancer in people, and fasting during cancer treatment belongs under the supervision of the oncology team.
Increase cellular turnover and regeneration. Fasting sends the body into cell recycling, a process of self-digestion at the cellular level called autophagy, in which damaged organelles and misfolded proteins are broken down and reused. Fasting and calorie restriction are among the most potent non-genetic triggers of autophagy (Bagherniya et al., 2018), although much of the direct evidence comes from animal and cell studies.
Support circadian rhythm and, for some people, sleep. Eating earlier in the day aligns meals with the body's circadian rhythms in metabolism (Sutton et al., 2018). The effect on sleep depends on the approach: a 2025 meta-analysis found that Ramadan fasting reduced sleep time and subjective sleep quality, while other time-restricted eating studies showed an overall increase in self-reported sleep time and no difference in sleep quality (Lima et al., 2025). Watching each client's sleep data is the best way to know which group they fall into.

Is It Working? Track It and See

The best way to understand how each client is responding to fasting, no matter which plan they're on, is with hard data. Fasting windows on their own tell only part of the story. The full picture comes from seeing them next to weight and body composition, glucose, ketones, sleep, heart rate variability and labs before, during and after a fasting protocol.

With Heads Up, you can run fasting as a program or protocol with adherence tracking, and review it alongside continuous glucose data from devices like Dexcom, ketone readings from Keto-Mojo, sleep and HRV from wearables like Oura, and lab results, all in one longitudinal patient record. Threshold alerts flag readings that need attention, such as low glucose, and clients log their data in the Heads Up companion app for iOS and Android. For more on what to measure, see our guide on how to track therapeutic fasting for best results, or try our free fasting timer.

See how Heads Up tracks fasting protocols and outcomes for your clients: request a demo.

Should Your Clients Fast?

With many metabolic benefits now backed by research, fasting can be a useful tool for many adults. It is not right for everyone, though. People who generally should not try intermittent fasting include children and teens, people who are pregnant or breastfeeding, people with diabetes or blood sugar problems, and people with a history of eating disorders (Johns Hopkins Medicine). For patients with diabetes, the main risk is hypoglycemia on glucose-lowering medications, and expert guidance suggests fasting can be done safely only under the supervision of their healthcare provider, with medication adjustments and glucose monitoring (Grajower and Horne, 2019).

Two other points are worth keeping in mind. First, intermittent fasting has been associated with a reduction in fat-free mass (Patikorn et al., 2021), so monitoring body composition and protein intake matters, especially for older clients. Second, an observational NHANES analysis found that an eating window shorter than 8 hours was associated with higher cardiovascular mortality. The authors noted that further research is needed to determine whether this reflects the short eating window itself or residual confounding (Chen et al., 2025). It cannot show cause and effect, but it is a reminder that long-term outcome data for fasting are still limited.

Not all fasting plans are right for everyone. Matching the protocol to the client, then tracking their key health stats during the fasting state, is the best indication of how fasting is working for them and how it affects their health day to day.

The big picture? For the right clients, fasting can become a steady, ongoing part of a healthy lifestyle plan for the long haul, rather than just a diet fad.

References

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11 Remarkable Health Benefits of Fasting