How can fasting help fight aging?

If you took everything people said intermittent fasting did as fact, this eating style would essentially be all of the most popular cosmetic procedures rolled into one—just available for free. Sadly, there's a lot of misinformation out there about fasting, its health benefits, and the science behind it. But is it the diet equivalent of Botox for all the systems of your body? Here's what you need to know about fasting, aging, and the quest for a longer lifespan.

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First of all, nothing can stop the aging process. As we've all heard countless times, death and taxes are the only guarantees in life. But there are a lot of claims about how intermittent fasting may slow aging or delay the aging process. It's an appealing idea, but we simply don't know enough right now to say that this anti-aging effect holds true in humans. Much of the research done on the anti-aging effects of fasting has been in animal models.

But we don't quite understand what's happening in animals that undergo fasting diets, either. There's a big difference between lifespan, the amount of time something lives, and healthspan, the amount of time something is healthy and functioning well, for example. Though mice who fast may live longer than their counterparts who don't, one study found that their quality of life may not improve (Xie, 2017). Fasting didn't appear to delay the onset of age-related symptoms in the research, which means the fasting mice simply lived longer with these conditions.

But other studies have found that fasting may enhance your body’s defenses against oxidative stress and promote the removal of damaged molecules. These effects may help with chronic diseases linked to inflammation, such as rheumatoid arthritis, heart disease, certain cancers, and even neurodegenerative diseases such as Alzheimer's disease. Unfortunately, we simply don't know whether it applies to humans or to what degree (de Cabo, 2019). 

There are many different styles of fasting, many of which have a goal of weight loss now—but that's not how this eating pattern started. Fasting originates from religion. Many religions have their own form of fasting, but they all involve abstaining in some way from food to show devotion. 

Many modern-day fasters are more devoted to anti-aging and their waistlines, but the concept is still the same, even across fasting styles. In all of these plans, there's some sort of caloric restriction for a defined period. Some fasting regimens include low-calorie intake days alternating with regular eating days. Other styles incorporate a fasting period into each day, so you eat your meals during a condensed window.

No matter the form of intermittent fasting you may have considered, you've likely seen the same health benefits getting a lot of lip service. There's lots of hype around fasting for its purported ability to aid in weight loss, control blood sugar by lowering insulin levels, decrease the risk of heart disease, improve metabolic rate, and even lengthen lifespan. But despite its long history, fasting is a relatively new concept in the research space. Many clinical trials are only preliminary, and there's a limit to what we can measure and, therefore, know at this point.

People get excited by the idea of autophagy when talking about fasting. Autophagy, which literally means "self-eating," is essentially a self-recycling of cellular waste. The idea is that when you're fasting, your body doesn't have to expend energy to break down and process food. With this excess energy, it can turn its attention “inward,” disposing of waste, cleaning, and healing areas within the body that otherwise wouldn't get the care. Researchers theorize that this type of autophagy may suppress tumors by cleaning out cancer cells and, therefore, aid in cancer prevention (Antunes, 2018). 

Although some scientists believe that, theoretically, autophagy slows with age and fasting may increase it, we have not yet verified these findings in humans. Additionally, we haven't fully clarified the mechanisms driving the longer lifespans in mouse studies and how they're tied to aging (Barbosa, 2019). Autophagy is an undeniably cool concept—but right now, most of the research is in animal models.

Fasting advocates will also mention hormesis as one of the benefits of intermittent fasting. Hormesis is the idea that small doses of potentially harmful things, whether calorie restriction or toxins, can increase our tolerance of that stressor (Deligiorgi, 2020). But again, most of the research is in animal models, and the findings may not apply to humans.

When talking about fasting, most people mean intermittent fasting—an alternating eating and fasting schedule. We all need to eat sometime. But you’ll find many different plans and regimens for how to incorporate intermittent fasting into your routine. There is no best fasting method for everyone—you need to consider your medical history and lifestyle. 

Typically, you either fast entirely on fasting days or have a very low-calorie intake (600 calories or less). Some of the more popular options: alternate-day fasting, periodic fasting, and time-restricted fasting (Wilhelmi de Toledo, 2021):

• Alternate day fasting (ADF): This regimen involves alternating between 24-hour fasting days and 24-hour regular eating days.

• Periodic fasting (PF):  An example of this type of fasting is the 5:2 diet, where you fast for two days per week (usually not consecutive days) and eat normally for the remaining five days. 

• Time-restricted fasting (TRF): TRF restricts your calorie intake to a specific “eating window.” A popular way to do this is to have a 16-hour fast and then eat all meals within an 8-hour eating window—this is also called 16:8 intermittent fasting. 

There is no best form of fasting—it is all about lifestyle fit. Given the significant number of unknowns in this emerging area of study, there's no reason to fast if it would be a dramatic lifestyle change from how you usually eat—unless your healthcare provider recommends intermittent fasting for a medical reason. 

But if you're curious about the health effects, lead a healthy lifestyle, and already have an easy time skipping meals, it may be worth a try. At this time, we cannot say fasting is safe for pregnant women, children, and older people, though. Be sure to discuss your potential fasting regimen with a medical professional, especially if you're taking any medication.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

October 25, 2021

Written by

Linnea Zielinski

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.