What Is the Optimal Fasting Length? (Hint: It’s NOT 16 Hours)
It’s no secret that intermittent fasting can be an effective tool for curbing cravings, reducing insulin resistance, and burning fat. What’s less obvious, however, is exactly how long you should abstain from eating or drinking in order to reap the most benefits of IF.
While conventional wisdom says a 16:8 protocol is the way to go, practicing a little more patience could lead to a more substantial payoff.
In a YouTube video published on Nov. 5, 2024, nutrition coach Thomas DeLauer delivered a full dose of IF wisdom, providing scientific evidence to support the notion that 16 hours is not the optimal fasting length.
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An IF Lesson From Thomas DeLauer
With almost 3.8 million YouTube subscribers and another 1.2 million followers on Instagram, DeLauer has amassed a loyal audience thanks to his ability to transform complicated science jargon into digestible bits of nutrition advice. In particular, his content focuses on two topics that often go hand-in-hand: the ketogenic diet and fasting.
Anyone remotely familiar with IF has likely heard that a 16:8 fasting-to-eating window is the gold standard. But adjusting that ratio to 20:4 — a.k.a. continuing to consume nothing for another four hours — is a worthwhile sacrifice, at least according to science.
Based on a study published in the Annual Review of Nutrition, DeLauer highlighted how, at 16 hours of fasting, the rate of gluconeogenesis (the metabolic process that produces glucose from non-carbohydrate sources) surpasses the rate of glycolysis. (1)
Why 20 Hours Is the Optimal Fasting Length
Staying on board that gluconeogenesis train a little longer can lead you to an even more rewarding destination. Citing a study published in the journal Metabolism, DeLauer emphasized just how much meat you may be leaving on the fat-burning bone by breaking your fast at the 15-hour mark.
“The difference between a 15-hour fast, as far as ketones are concerned, and a 20-hour fast could literally be double the amount of ketones,” he explained.
Essentially, it all boils down to taking advantage of that gluconeogenesis ramp-up around the 15- to 16-hour mark. That’s when ketone production increases, paving the way for several potential health benefits.
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Breaking Your Fast
When you’re finally ready to eat, DeLauer recommends starting with bone broth, followed by a small amount of lean, low-fat protein. You can start consuming more food a couple hours later.
How you structure your eating window depends on your lifestyle and goals. But according to DeLauer, just like there’s an optimal fasting length, there’s an optimal time if you’re focused on building muscle.
“I would recommend that you shift your eating window so that you’re eating in the morning and fasting from morning to morning vs. evening to evening,” he explained.
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References
- Cahill, G. F. (2006). Fuel metabolism in starvation. Annual Review of Nutrition, 26(1), 1–22. https://doi.org/10.1146/annurev.nutr.26.061505.111258
- Kolb, H., Kempf, K., Röhling, M. et al. Ketone bodies: from enemy to friend and guardian angel. BMC Med 19, 313 (2021). https://doi.org/10.1186/s12916-021-02185-0
Featured Image: @Pormezz / Shutterstock
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