Overview of Fasting Compilation: Leading Experts On Water-Only Fasts, Fasting Mimicking Diets & The Optimal Fasting Window For Longevity
This episode is a curated compilation of conversations hosted by Rich Roll with leading fasting experts — Dr. Alan Goldhammer (medically supervised water-only fasting), Dr. Valter Longo (fasting-mimicking diet / longevity research), Dr. Michael Greger (nutrition & time‑restricted eating), plus references to researchers like Sachin Panda and Luigi Fontana. The show compares different fasting approaches (daily time‑restricted eating, intermittent/alternate‑day fasting, multi‑day water-only fasts, and fasting‑mimicking diets), summarizes their physiological effects, practical protocols, safety considerations, who benefits most, and how to apply these tools for metabolic health and longevity.
Key takeaways
- Daily time‑restricted eating (about 12 hours eating / 12 hours fasting) is widely recommended as safe, practical, and beneficial for most people.
- Early time‑restricted feeding (concentrating calories earlier in the day) appears metabolically superior to a late‑eating window.
- Fasting‑mimicking diets (FMDs) — multi‑day, calorie‑restricted, plant‑based kits designed to trigger fasting biology — offer an approachable middle ground with clinical data across conditions (diabetes, cancer adjunctive use, neurodegeneration, autoimmunity).
- Prolonged medically supervised water‑only fasting can produce dramatic clinical improvements for certain “hard cases” (hypertension, type 2 diabetes, autoimmune disease, some cancers) but requires medical oversight and careful medication withdrawal.
- Mechanistically, fasting preferentially mobilizes visceral fat, lowers blood pressure via natriuresis, reduces pro‑growth signals (IGF‑1), improves insulin sensitivity, mobilizes fat‑soluble toxins, and induces beneficial enzymatic and metabolic adaptations.
- Safety and long‑term outcomes vary by protocol; individualization and clinical monitoring matter.
Experts & perspectives
Dr. Alan Goldhammer (medically supervised water-only fasting)
- Focus: therapeutic, water‑only fasting in a medically supervised inpatient/outpatient setting.
- Typical protocols: 5–40 days water‑only fasts; recovery period ≈ half the fasting duration with monitored refeeding. Many clinic patients fast 2–3 weeks.
- Candidacy: best for “hard cases” who haven’t responded to diet/meds (severe hypertension, insulin‑resistant T2D, autoimmune disease, some lymphomas). Not for those who can’t safely withdraw medications or are severely frail/unstable.
- Clinical claims: significant reductions (often elimination) in medication needs, large drops in blood pressure, preferential visceral fat loss (DEXA data), robust natriuresis.
- Safety: published safety data from his clinic; close monitoring (twice‑daily exams, labs, urinalysis) and staged medication tapering are essential.
Dr. Valter (Walter) Longo (fasting‑mimicking diet & longevity)
- Focus: FMD — plant‑based, low calorie/protein, higher relative plant fats — designed to physiologically mimic fasting for 4–7 days depending on indication.
- Protocols: typical FMD cycles last 4–7 days (4 days for some cancer adjunct protocols, 5 for general users, 7 for certain autoimmune protocols). Frequency: often 2–4 cycles/year for general use; diabetes trial used monthly cycles for 12 months.
- Rationale: FMDs reproduce key fasting biomarkers (lower IGF‑1, improved insulin sensitivity) without complete food abstinence and with better safety/adherence for many people.
- Position on intermittent/alternate‑day fasting: cautious about alternate‑day and 5:2 approaches for broad public use due to adherence and unknown long‑term effects; favors time‑restricted eating + periodic FMD cycles.
Dr. Michael Greger (nutrition & time‑restricted eating)
- Focus: nutrient density, caloric dilution strategies, timing of eating.
- Recommendation: time‑restricted eating (≤12 hours eating window) and emphasis on early eating (breakfast ≠ expendable). Notes early TRF can synergize with circadian biology to improve metabolic outcomes, sleep, and weight control.
- Practical tips: water preloading, high fiber/water‑rich plant foods, the “Daily Dozen” dietary checklist to ensure nutrient density.
Mechanisms & documented effects
- Preferential visceral fat mobilization: DEXA data reported — e.g., a 2‑week fast may reduce a disproportionate share of visceral fat (examples cited: ~20% total fat loss with ~55% visceral fat loss in a typical male).
- Natriuresis: rapid, selective sodium loss during water fasting contributes to early fluid weight loss and marked blood pressure reductions (comparable to or greater than diuretics).
- Reduced IGF‑1 and sustained metabolic switching: multi‑day fasting/FMD cycles can lower IGF‑1 and leptin for months and shift metabolism toward increased fat utilization and insulin sensitivity.
- Detoxification: fasting mobilizes fat‑soluble chemicals stored in adipose tissue (PCBs, dioxins, heavy metals) — clinical significance and required management debated but measurable reductions in some studies have been documented.
- Enzymatic induction: repeated fasting can induce metabolic enzyme systems (gluconeogenesis, lipolysis), analogous to training adaptations.
- Circadian timing: eating earlier in the day aligns with circadian rhythms (temperature, cortisol/testosterone cycles) and appears to improve metabolic outcomes vs. late-night eating.
Safety, contraindications & practical monitoring
- Do NOT attempt prolonged (multi‑day) water‑only fasting without medical supervision if you:
- Are on medications that cannot be safely withdrawn (e.g., anticoagulants after recent PE/AF, some cardiac meds).
- Have anorexia, severe cachexia, or are actively losing weight for oncologic reasons without clinician oversight.
- Are pregnant, breastfeeding, or severely frail/elderly without careful modification.
- Medication management: many drugs require dose adjustment or tapering when dietary patterns change; fasting potentiates some medications — supervised withdrawal and monitoring required.
- Monitoring protocol in clinics: frequent clinical checks, labs, urinalysis, and staged refeeding; safety studies from experienced centers report high rates of safe completion but occasional hospitalizations.
- Refeeding: critical to follow a healthy refeeding strategy (in these experts’ clinics, typically whole‑plant, SOS‑free — i.e., low Salt/Oil/Sugar) to consolidate fat loss and avoid adverse effects.
Practical, evidence‑based recommendations (actionable)
- Start simple: adopt a 12:12 daily time‑restricted eating window (eat over ~12 hours, fast ~12 hours). This is safe and effective for most.
- Favor early windows: align the feeding window earlier in the day when possible (largest meal at lunch/early afternoon rather than late at night).
- Improve diet quality: emphasize nutrient‑dense, whole plant foods; reduce processed foods, added salt/oil/sugar.
- For additional metabolic/aging benefits consider:
- Periodic FMD cycles (4–7 days) — frequency often 2–4×/year; people with diabetes were trialed monthly cycles in research contexts.
- Intermittent 16:8 daily fasting may be useful for some, but be mindful of late‑eating and long‑term unknowns.
- If considering multi‑day water‑only fasting for disease reversal:
- Seek a reputable medically supervised clinic.
- Undergo full medical assessment, medication review, and follow supervised tapering and refeeding.
- Track outcomes: monitor blood pressure, glucose/A1c, lipids, body composition (DEXA if available), sleep quality, and symptoms.
- Sleep and stress: normalize sleep (avoid food in the last ~3 hours before bed when possible), and manage stress as part of the overall strategy.
Who benefits most
- Candidates for FMD or supervised multi‑day fasting: people with treatment‑resistant metabolic disease (hypertension, T2D), certain autoimmune disorders, and select oncology adjunct cases — especially when traditional interventions have failed.
- General public: 12:12 time‑restricted eating + whole‑food plant emphasis is broadly applicable, low risk, and supports weight control and metabolic health.
- Not good candidates: people who require uninterrupted medication (e.g., certain anticoagulants), active eating disorder, or severe frailty without program modification.
Notable quotes from the episode
- “When it’s needed, there’s nothing else that does exactly what water‑only fasting does.” — Dr. Alan Goldhammer
- “Eat for 11 hours or 12 and fast for 13 hours or 12.” — Dr. Valter Longo (practical phrasing supporting a ~12:12 window)
- “If you want to be healthy you gotta pay the price and live healthfully: diet, exercise, sleep, daily fasting, occasional prolonged fasts — and manage stress.” — Dr. Alan Goldhammer
Limitations & open questions
- Long‑term effects of alternate‑day fasting and frequent prolonged ketotic states are not fully established; some meta‑analyses raise concerns about long‑term mortality for certain extreme patterns.
- Precise optimal window (12 vs. 16 vs. early/late) and personalization factors (age, sex, chronotype) require more large‑scale human trials.
- The mechanisms by which fasting mobilizes specific tissues and toxins are being actively researched; translational work and fasting‑mimicking drugs are areas of industry interest.
Quick starter checklist
- Try a 12:12 daily window for 2–4 weeks; move mealtimes earlier if possible.
- Increase whole‑plant food intake; reduce processed foods, added salt, oil, sugar.
- Improve sleep hygiene; avoid meals within ~2–3 hours of bedtime.
- If considering multi‑day interventions (FMD or water‑only fasting): consult your primary care physician; research reputable supervised programs; plan medication review and post‑fast refeeding strategy.
- Monitor BP, glucose, and symptoms; seek medical help for dizziness, severe fatigue, or concerning signs during prolonged fasts.
For readers who want to dive deeper, each highlighted guest (Goldhammer, Longo, Greger) has additional literature, clinical trials, and books (e.g., Valter Longo’s The Longevity Diet) referenced in the episode.