Does Intermittent Fasting Increase Longevity?

New research offers good reason to be skeptical

Welcome back to Age Wise, exploring the science of improving physical health and mental wellness at every stage of life. This week, new research takes a dim view of an old claim.

Intermittent fasting has been widely touted as a healthy way to lose weight and improve health, increase performance of the brain and body, and extend life—all by extending the number of off-hours on food consumption. There are many variations. One modest approach is to stop eating early in the evening and not eat again until, say, late morning—confining food consumption to 12-hours or less. More extreme approaches restrict the eating window to just six hours a day, or even encourage skipping food for entire days.

The idea is that your body benefits from the break, in part by turning off the digestive system.

It makes a lot of sense when you consider that our natural body clock, our circadian rhythm, is tuned not just to daylight and darkness but other cues, too, including ambient temperature, stress and anxiety, and food intake. Allowing several hours between your last meal and bedtime can indeed be good for sleep.

Among the things you might really want to cut back on? Image: Pexels/Andrea Piacquadio

But if you count on intermittent fasting to lose weight, you’ll likely be disappointed. New research published in the Journal of the American Heart Association finds eating less overall, and fewer large meals, works better for managing weight than restricting eating to a narrow time window.

Beyond that, one important measure of the benefits of intermittent fasting ought to be longevity. If a certain behavior is good for health, then people who adhere to it ought to live longer, on average, compared to those who don’t. The time-restricted eating fad hasn’t been around long enough to enable a lot of thorough tests of this on humans, many of whom, I’m guessing, also don’t want to be lab rats and participate in highly controlled tests about this.

So for now, despite many armchair scientists’ claims, intermittent fasting has not been proven successful for longevity. In addition to the above-noted challenges in sussing out any benefits is the fact that a restricted eating window can cause people to consume fewer calories overall, an obviously important variable that has to be accounted for in any analysis of possible benefits.

That’s why I’m interested in a recent study that suggests intermittent fasting might not increase lifespan. In the research, published last month in the journal Nature Communications, scientists used mice to examine the long-term effects of intermittent fasting and two other approaches thought by some to slow aging in humans.

(I don’t normally report on studies done on mice, because they do not always reflect what’s ultimately found to be the case in humans. But rodents are good analogues for the biology of humans, and it’s worth making exceptions when the results can help inform important human health topics that otherwise lack robust research or firm conclusions—as with intermittent fasting.)

The study was highly complex, so I’ll stick to the conclusion: Intermittent fasting and the other methods analyzed “proved largely ineffective in their supposed impact on aging.” 

Let’s not put too much weight in one study done on mice. But I like the upshot, delivered by study team member Dan Ehninger, a senior scientist at the German Center for Neurodegenerative Diseases: "There is no internal clock of aging that you can regulate with a simple switch - at least not in the form of the treatments studied here.”

Simply put: You will get older, and there’s no cure for aging. But you can do smart things to up your odds of aging well and staying healthy and capable throughout your existence. While the jury remains out on the potential benefits of intermittent fasting—and they might be significant—here’s what we can say for sure:

Instead of silver bullets, anyone wishing to live long and well would be wise to consider a range of lifestyle and behavioral choices, including of course physical activity. And there are two aspects of your diet that are definitely known to improve the chances of good health and longer life: Develop a healthy way of eating, and eat less. Blocking out a long stretch at night when you don’t eat—say 6 or 7 p.m. to 8 or 9 a.m. or whatever works for you—might help you eat less overall and—this is important—avoid late-night snacks. Such a scheme would help you sleep well, literally and figuratively, in the knowledge that you’re benefitting from a bit of intermittent fasting. 

And better sleep—as you might know from my book—is definitely a path to better health and longevity.

Totally unrelated, here are my latest articles on Medium:

• The Best Music for Sleep Playlists

• The Recipe for a ‘Seasoned Human’

• Really Short Breaks from Sitting Yield Big Mental and Physical Benefits

• Wow! The Awe-Inspiring Health Benefits of Sunrises and Sunsets

Also, if you are using Mastodon (the less toxic Twitter alternative) you’ll find me publishing health news briefs there that I don’t publish elsewhere. I’m at me.dm/@robertroybritt.

Take care of yourself, now and again.
—Rob

Your support makes this free newsletter possible. If you find it useful, please consider forwarding it to someone who might benefit. You can find more of my health and wellness writing on Medium. Also find me on YouTube, Instagram, Twitter, Linkedin. And if you ever feel tired, unfocused, stressed or cranky in the afternoon, check out my book, Make Sleep Your Superpower.