What Are The Long-Term Effects Of Daily Intermittent Fasting?
IF Insider No. 52
In our last issue (IF Insider No. 51) we look at fermented foods, a group of foods that have the very real potential to supercharge your nutrition as well as your intermittent fasting practice. In this issue, we are going to explore a question that we frequently get from our Fast Factor Circle members: What are the long-term effects of daily intermittent fasting?
What underlies that question is another, deeper concern: What is daily intermittent fasting going to do for (or to) my health in the long run? Is it safe to continue practicing daily over many months or even years?
For our premium subscribers, in this week’s Research Spotlight, we are going to look at an exciting study that examines the additive effect of combining intermittent fasting with caloric restriction and what these findings could mean for you in practical terms. Hint: It’s got to do with longevity!
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Is Long Term Intermittent Fasting Good For Your Health Or Is It Potentially Harmful?
In attempting to answer this question, I do what I usually do: I search the scientific literature for studies to get my answers. In this case, all I got was mass confusion and no real answers!
For one thing, no one really agrees on just one definition of intermittent fasting, and different studies use different definitions. This makes comparing studies difficult if not impossible. In a 2022 review article, Intermittent Fasting and Metabolic Health, published in the journal Nutrition, the authors state:
“Intermittent fasting, on the other hand, refers to eating patterns that target a pattern of dedicated periods of time (ranging from 12 h to several days) with consumption of little or no calories . It is voluntary, has a fixed duration, and caloric drinks are consumed regularly.”
Fasting for several days? Regular consumption of caloric drinks?? This is certainly not our definition of intermittent fasting, which has always been a daily period of no food consumption within a 24-hour time frame. During that time you can have unlimited amounts of unflavored and unsweetened (either naturally or artificially) water (plain or sparkling), plain black or green tea or black coffee, again unflavored and unsweetened.
We don’t advocate restricting calories during your “feasting” time but do suggest that you eat until you are satisfied, not stuffed. There are no absolutely “off limits” foods, but we do encourage you to eat a well-balanced healthy diet with little to no processed foods or refined sugar and plenty of healthy fats.
We recommend that beginners start with a 16:8 protocol, meaning 16 hours of fasting and an 8-hour window in which to consume food. If 16:8 is too difficult, you can back up and begin with 14:10 or even 12:12. Some people have great success with 16:8 as their schedule and others find it necessary to increase the fasting period to somewhere around 18:6 or so.
Almost all of the studies I looked at stated there was just not enough research out there to say if intermittent fasting is safe and effective over the long term and all said that more long-term studies are needed.
What does have plenty of evidence is intermittent fasting’s ability to improve cardio-metabolic health as well as a host of other health benefits. And what is not in dispute is the harmful effects of our current Western way of eating, consisting of basically eating whatever you want and whenever you want it, with no periods of digestive or metabolic rest in between.
This way of eating has led to an absolute epidemic of “modern” diseases including cancer, Alzheimer’s, diabetes, obesity, fatty liver disease, autoimmune disorders, and more. People who are critical of intermittent fasting are quick to point out that it’s somehow dangerous because you can’t be sure you are getting enough protein, vitamins, calories, and the like. These same critics are silent when it comes to results of the typical diet that most Americans eat every single day of their lives, without much thought of the nutrients, or lack thereof, they are consuming.
I came to this question, as I do with all questions…with an open mind. If multiple scientific studies were to show that something is harmful, then I am prepared to accept that. Even if it means radically changing my current beliefs. But this is not the case here. There are no long-term studies, and there is also no current convincing evidence of harm from intermittent fasting, at least the way Denise and I do it.
If you have concerns, we would also refer you back to our IF Insider No. 44 - Intermittent Fasting: A Deep-Dive Review of the Basics - Benefits and Biology and to the positive review article, Effects of Intermittent Fasting on Health, Aging, and Disease, published December 26, 2019, in the New England Journal of Medicine.
Anecdotally, daily intermittent fasting is still working well for us, as well as clients and friends, with no apparent untoward effects. So until I can see something to the contrary, I say…fast on!
Vasim, I., Majeed, C. N., & DeBoer, M. D. (2022). Intermittent Fasting and Metabolic Health. Nutrients, 14(3), 631. https://doi.org/10.3390/nu14030631
Why It Matters
“We are wired for feast and famine, not feast, feast, feast.”
~ Jason Fung, MD - Physician, author and researcher who advocates intermittent fasting. His science-based books about diabetes and obesity go against conventional wisdom that says type 2 diabetics are doomed to a life with an incurable disease.
What We Are Reading 📚
With each issue, we bring you a short blurb on what we are currently reading or watching, including books, articles, podcasts, videos, movies, and research papers of value.
Denise - This article - Aging Wisely - by Sharon Salzberg on the Ten Percent Happier site, really hit home for me. Aging well and working towards a longer healthspan involves more than how you eat and move. It’s a mental game, too.
It’s about learning to let go, accept, and embrace change. Salzberg’s latest book is Real Change and I just added it to my reading list so I can explore these concepts more deeply.
Ellen - I am revisiting M.F.K. Fisher’s (1908-1992) The Art of Eating, originally published in 1954 and republished many times since then, with the 50th-anniversary edition published in 2014. Not exactly a cookbook, The Art of Eating, a collection of the author’s essays, is a love poem to eating, and her writing is all at once witty, sarcastic, opinionated, and beautiful.
As a child in the rural South, she introduced me to a world of food and tastes that seemed like they belonged to another era, if not from another planet entirely! If you have never indulged yourself in her writing, please give yourself the gift of looking at food and cooking in a way you never thought was possible.
Did you like this article and learn something new? If so, please let us know in the comments! Questions and suggestions for future articles are welcome, too!
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