This Scientist Warns Against 16:8 Fasting (and how to fast properly)

Summary

The conversation challenges the idea that fasting is automatically beneficial or harmful. Joel Green’s central point is that biological effects often follow a U-shaped curve: a practice may help at an appropriate level but become counterproductive when it is too intense or prolonged. The speakers apply this idea to fasting and the gut bacterium Akkermansia muciniphila.

Key wellness strategies and ideas

• Treat fasting as individual and dose-dependent. Consider duration, frequency, diet, activity, and personal response—not just the fasting window. The discussion cautions against treating 16:8 as a universally suitable daily protocol.
• Consider gut-fiber intake during prolonged fasting. Green says Akkermansia can use dietary materials, such as polyphenols and resistant starch, or the mucus lining the gut. If dietary substrates are scarce for a long time, he argues, the bacterium may rely more on the mucus layer. The speakers emphasize that the effect depends on context and balance.
• Pair fasting with movement and food-seeking activity. Their picture of fasting in nature is not sitting still while hungry; it involves activity and occasional access to small amounts of foraged foods. They distinguish this from repeatedly snacking while sedentary.
• Consider an “amplified fast” approach, as described by Green. The day before a fast, he suggests including a variety of plant foods—such as berries, roots, resistant-starch foods, and cruciferous vegetables—to provide microbiome substrates. He presents this as a way to prepare for fasting, not as a strict or universally proven protocol.
• Favor dietary variety over daily reliance on a single food or supplement. Green argues that gut microbes benefit from varied food sources and that products marketed for daily use are not automatically necessary every day. He advises focusing on food sources and appropriate amounts rather than assuming more is better.
• Pay attention to how fasting affects eating afterward. Green describes developing strong overeating urges after fasting and says some people may experience this response. If fasting triggers intense rebound eating or feels unsustainable, that is a reason to reconsider the approach rather than push through.
• For post-fast overeating, Green describes a specific strategy: an early, substantial meal with protein and carbohydrates, vitamin D, and fermentable fiber, intended to support appetite and circadian signals. This is his proposed method, not a general clinical recommendation.
• Think beyond calories alone. The speakers discuss calories as one part of weight regulation, alongside hormones, metabolism, and other health factors. They also caution that calorie-focused plans may not work the same way for everyone.
• Be cautious about “more is better” supplement thinking. The conversation argues that timing and dose matter for supplements and antioxidants, and that taking them routinely may not always be beneficial. It also briefly promotes an electrolyte drink; this is a product mention rather than a core fasting recommendation.

The discussion presents these points as a framework for thinking about fasting, not as individualized medical advice. The subtitles do not provide complete citations for the studies mentioned.

Presenters and sources mentioned

• Presenters: Thomas DeLauer and Joel Green.
• Sources or research referenced: A Swedish study involving about 4,200 people; research attributed to Francisco Albi; Kevin Hall’s metabolic-ward studies; Harvard research on brain changes after weight loss; and the TV show Alone. Green also refers to his book and an appearance on the Ben Greenfield podcast; the full titles and citations are unclear in the subtitles.