Why 16:8 Fasting Is DESTROYING Your Metabolism (Do This Instead)

Summary

Dr. Michael Diamonds argues that fasting may be harder to sustain if someone immediately adopts a long fasting window while sharply reducing calories. He recommends gradually narrowing the eating window, which he says may make hunger easier to manage.

He attributes the difficulty of aggressive fasting to stress responses involving cortisol and insulin. He also uses a “balloon” analogy, suggesting that the stomach and hunger patterns need time to adjust to a shorter eating window.

Strategies and stages

He recommends moving to the next stage only when the current one feels manageable, rather than jumping straight to a 16:8 or 18:6 schedule.

Stage Suggested eating window Suggested calorie range 12:12 8 a.m.–8 p.m. About 1,800–2,000+ 14:10 10 a.m.–8 p.m. About 1,600–1,800 16:8 Noon–8 p.m. About 1,400–1,600 18:6 2 p.m.–8 p.m. About 1,200–1,400 20:4 4 p.m.–8 p.m. About 1,100–1,300

For the 12:12 stage, he also recommends reducing grazing and snacking. He describes 20:4 as an optional, brief stage for some people.

Considerations

• Calorie targets are individual. These ranges are part of the presenter’s method and should not be assumed appropriate for everyone. Very low calorie intake or extended fasting may be unsuitable without professional guidance.
• Prioritize hunger and sustainability. He advises progressing only when the current schedule feels manageable, rather than relying on willpower to endure strong hunger.
• Account for personal health needs. The video mentions perimenopause, thyroid issues, and a history of crash dieting as reasons someone may need an individualized plan.
• Seek qualified medical advice when needed. The video makes claims about hormones, metabolism, and fasting benefits. These claims and calorie ranges reflect the presenter’s account and are not personalized medical advice. Consult a qualified clinician before making significant dietary changes.

The video also promotes a free fasting guide and paid coaching through Sculpt by Science.

Presenters and sources

• Presenter: Dr. Michael Diamonds, also called Dr. Mike
• Other clinicians named: Dr. Zeno (name as transcribed), Dr. Angela, Dr. Penelope, and Dr. Kelsey, described as part of the Sculpt by Science team
• Research sources cited in the video: Cell Metabolism; Cell Reports Medicine; New England Journal of Medicine; Endocrine Reviews (Le Fontan and colleagues, as transcribed); and Journal of Obesity (Stubbs and colleagues)