Intermittent fasting: Is it all it’s cracked up to be?



Intermittent fasting is an increasingly popular weight loss dieting strategy. Beyond weight loss however, the diet has promising benefits that may reduce the risk of developing some chronic, lifestyle diseases. In this Honest Nutrition feature, we explain all that you need to know about intermittent fasting, and whether it is worth the hype.

Written by Amber Charles Alexis, MSPH, RDN on May 27, 2022 — Fact checked by Alexandra Sanfins, Ph.D.

This series of Special Features takes an in-depth look at the science behind some of the most debated nutrition-related topics, weighing in on the facts and debunking the myths.

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Intermittent fasting is a term used to describe a variety of eating patterns that have alternating periods of fasting — abstinence from foods — and eating.

The fasting period may last from 12 hours per day to several consecutive days, with a consistent, recurring pattern over the course of a week.

The main typesTrusted Source of intermittent fasting are modified fasting or the 5:2 diet — this protocol involves fasting for 2 non-consecutive days of the week, and eating normally for 5 days alternate-day fasting — fasting days are alternated with days where foods and beverages are consumed normally, without restrictions time-restricted eating — a type of intermittent fasting that limits the “eating window” to 4–12 hours, inducing a daily fasting period of 12–20 hours. Persons eat to satiety during their eating windows without caloric restrictions. Of these, time-restricted eatingTrusted Source is the most popular, and may be what most people refer to when they mention intermittent fasting.

The 16:8 pattern — eating during an 8-hour window and fasting for 16 hours each day — may be the most recommended time-restricted eating pattern.

The circadian rhythm Much of the research on intermittent fasting and time-restricted eating considers the impact of fasting on the body’s natural circadian rhythm.

The circadian rhythmTrusted Source, also called the circadian clock, represents the 24-hour cycle of metabolism in the body, including control of the sleep-wake cycle, blood pressure, mood regulation, and hormonal balance, to name a few.