McCall McPhersonFounder, Modern Thyroid Clinic.

Understanding the Effects of Fasting on Longevity

13 Apr 2025 · 0 min

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A short conversational excerpt from a YouTube video in which host McCall McPherson asks whether intermittent short water fasts (36–48 hours) can trigger longevity-related mechanisms without the harms of major caloric restriction. Speaker A cites laboratory animal experiments (short-term fasting and every-other-day feeding) suggesting benefits can be offset if subjects overeat on non-fasting days. Speaker A frames fasting and time-restricted eating (e.g., 16/8 or 12/12) as practical tools to limit intake and possibly improve circadian rhythm, but warns that overeating undermines their benefits according to animal data.

Take significant caloric restriction off the table, but know it can influence some of these mechanisms of longevity. Would something potentially like a short ish water fast of 36 or 48 hours intermittently propagate the same response without the deleterious effects?
What I can say is in laboratory animals people have tried to do these experiments, so they've done short term fasting or even every other day feeding. Right. For, for months or years. Okay, so that would suggest that the, the, the overeating, let's just call it overeating on the days where they're eating offsets the benefits you get from fasting. So I think of fasting and time restricted eating, which would be like 16 or 8, 16 or 12, 12, whatever. I think of those as useful tools that at a minimum can help some people control how much they're eating. I think for some people it can also have a benefit on their circadian rhythm, which is a different discussion but also important for health. But if you aren't, if they, if, if you are overeating, I don't think that fasting or time restricted feeding gives you any benefits, at least based on what we know in the animal studies.
Cool. I love it. Thank you.