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

What happened in this episode?

Thomas DeLauer interviews nutrition researcher Joel Greene about potential downsides of routine intermittent fasting—particularly daily 16:8—and how fasting might be made more “nature-aligned”. Greene argues that many biological effects sit on a U-shaped “Goldilocks” curve, where an intervention can be beneficial at one dose and harmful at another, and applies this to the gut bacterium Akkermansia muciniphila, which can feed on dietary substrates but also on the gut mucus layer.

Greene claims that prolonged fasting or very low-fibre eating can leave Akkermansia with fewer dietary substrates and may encourage erosion of the gut mucosal layer over time. He cites what he describes as a 2026 Swedish study of about 4,200 participants linking elevated Akkermansia, when combined with low-fibre diets, to higher likelihood of type 2 diabetes. He also alleges newer evidence that antibiotics may leave behind mutated Akkermansia strains that become overrepresented during recovery.

A recurring theme is Greene’s criticism of “daily” supplement-style thinking applied to microbiome products; he says diet diversity and intermittent exposure, rather than constant dosing, better fits human biology. In a personal account, Greene says years of fasting have left him susceptible to hyperphagia, making 24-hour fasts difficult, and he outlines a protocol he says can help curb it involving an early large meal, vitamin D, and fermentable fibre. The episode also includes a brief promotion by DeLauer for LMNT electrolyte drinks.

What are the key points?

• Greene says fasting can increase Akkermansia muciniphila, but argues excessive or context-free increases may contribute to gut mucus-layer degradation.
• He cites an unverified description of a 2026 Swedish study (~4,200 participants) linking elevated Akkermansia plus low fibre with higher likelihood of type 2 diabetes.
• Greene argues fasting should be paired with ‘foraging’ foods (berries, resistant starches, polyphenols) to provide microbial substrates similar to what would be available during food-seeking in nature.
• He criticises ‘daily’ microbiome supplements as a commerce-driven model that ignores dosing, frequency and context.
• Greene says he can no longer complete 24-hour fasts due to hyperphagia after years of fasting; DeLauer says he has noticed similar patterns.
• Greene outlines a hunger ‘reset’ approach involving an early large breakfast with protein and carbohydrates, vitamin D and fermentable fibre, framed as circadian and appetite signalling support.

Who is speaking?

Named speakers identified in Egleze's source-linked moments from this episode.

• Joel Green

Which topics are covered?

How is this page sourced?

Programme

Thomas DeLauer

Duration

53m

Original episode

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