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If you took everything people said intermittent fasting did as fact, this style of eating 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, the health benefits of fasting, and even what we know about 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 and the quest for a longer lifespan.
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. Modern-day fasters are more devoted to their 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. Some fasting regimens include low-calorie intake some days and normal intake alternating days, while other styles incorporate some fasting period into each day, so meals are eaten during a condensed window of opportunity.
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.
- There are many different forms of fasting, but they all involve calorie restriction for periods of time.
- Fasting may improve blood sugar, lower risk of cardiovascular disease, and aid weight loss.
- Advocates for this style of eating also claim it may have anti-aging effects.
- Some studies do show that animals that fast live longer than those that do not.
- Many of the health benefits of fasting are said to come from autophagy—a process kicked off by fasting that may help clear the body of cellular waste.
- But there’s a lot we don’t know about how fasting affects humans.
Can fasting stop or slow the aging process?
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 actually holds true in humans. Much of the research done on anti-aging and different forms of fasting has been conducted in animal models.
But we don’t even 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, their quality of life may not improve, one study found (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 down-regulate gene expression of more than 50 pro-inflammatory genes (Higami, 2006). This may decrease the risk of chronic diseases linked to inflammation such as rheumatoid arthritis, certain cancers, and even neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease—but we simply don’t know whether it holds true in humans or to what degree. So though the findings are exciting, researchers such as Krista A. Varady, Ph.D.—who has been researching alternate-day fasting for 15 years—urge caution when interpreting how these findings may benefit human health.
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The theory of autophagy
People get really 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 be able to suppress tumors by cleaning out cancer cells and, therefore, aid in cancer prevention (Antunes, 2018).
It’s also believed that it’s through autophagy that we’re able to use stored nutrients as an energy source (Kaur, 2015), which is where advocates of fasting get the idea that it’s somehow “better” for weight loss than any other plan that includes calorie restriction. Autophagy is an undeniably cool concept—but right now we can only measure it in worms. So though we know that theoretically autophagy slows with age and fasting may increase it, we can’t verify these findings in humans (Barbosa, 2019).
And there are a couple of unknowns being ignored when anyone claims one of the effects of fasting is increased autophagy, and in that way, this style of eating leads to a longer lifespan. Past studies have failed to show that ramping up one aspect of gene expression tied to autophagy can actually extend lifespan. Additionally, we haven’t fully clarified the mechanisms driving the longer lifespans in mouse studies and how they’re tied to aging (Barbosa, 2019). This cellular cleaning process isn’t reliant on fasting, either. Different forms of stress can activate some degree of autophagy, fasting being one example and exercise being another (He, 2012).
The hormetic effect of fasting
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 it’s calorie restriction or toxins, can increase our tolerance of that stressor. There’s even some indication that cells may overcompensate for mild stressors, and that this can lead to a beneficial effect on aging and longevity. Past studies have observed a delay in age-related diseases associated with exposure to calorie restriction in animals, as long as malnutrition is avoided (Kouda, 2010). But again, these are animal models, and the findings may not hold true in humans.
When we talked to Dr. Varady about the best form of fasting, she underscored that it’s all about lifestyle fit. Given the great number of unknowns in this emerging area of study, there’s no reason you need to fast if it would be a dramatic lifestyle change from how you usually eat—unless your healthcare provider is prescribing this particular form of dietary restriction 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 fast with a medical professional if you’re taking any medication.