Rankings / Comparisons
Extended fasting (24-72h+) vs Fasting-mimicking diet (FMD / ProLon)
Water-only extended fasting vs a low-calorie diet that mimics it — what trades off in the autophagy/refeeding window.
Reviewed by Read Off Label · How we grade
Bottom line
On the composite score, Fasting-mimicking diet (FMD / ProLon) (B-, 6.3/10) edges out Extended fasting (24-72h+) (C, 4.6/10) — but the right pick depends on the specific outcome you're optimising for.
- Evidence
- Moderate-Preclinical (4/10)
- Benefit
- Varies (5/10)
- Risk
- Med (refeeding syndrome after longer fasts; electrolyte monitoring; muscle loss) (5/10 safety)
- Legality
- N/A
- Dose
- 24-72h periodic; electrolytes (Na/K/Mg) essential; break gently; quarterly to annually
- Class
- Protocol
- Last reviewed
- Jun 8, 2026
Read Off Label grades Extended fasting (24-72h+) as C (4.6/10) based on moderate-preclinical evidence, variable benefit magnitude, and a med-risk safety profile.
Cheng/Longo work shows hematopoietic stem cell regeneration with 3-day fasts in mice (human data less mature).
Typical use: 24-72h periodic; electrolytes (Na/K/Mg) essential; break gently; quarterly to annually — N/A.
What it is
Cheng/Longo work shows hematopoietic stem cell regeneration with 3-day fasts in mice (human data less mature). Risk rises rapidly past 72 hours without supervision. Water-only vs bone broth protocols differ.
Mechanism
Deep ketosis; extensive autophagy; stem cell mobilization (Longo); growth hormone elevation; complete insulin suppression; hematopoietic regeneration signals
Full Extended fasting (24-72h+) review →
- Evidence
- Moderate (6/10)
- Benefit
- Med (5/10)
- Risk
- Low-Med (7/10 safety)
- Legality
- Commercial (ProLon) or DIY
- Dose
- 5 days monthly; ~1100 kcal day 1, ~750 kcal days 2-5; very low protein/carb
- Class
- Protocol
- Last reviewed
- Jun 8, 2026
Read Off Label grades Fasting-mimicking diet (FMD / ProLon) as B- (6.3/10) based on moderate evidence, med benefit magnitude, and a low-med-risk safety profile.
Longo/Wei 2017 trial: 3 monthly cycles reduced biological age markers, BMI, blood pressure, IGF-1 in humans.
Typical use: 5 days monthly; ~1100 kcal day 1, ~750 kcal days 2-5; very low protein/carb — Commercial (ProLon) or DIY.
What it is
Longo/Wei 2017 trial: 3 monthly cycles reduced biological age markers, BMI, blood pressure, IGF-1 in humans. Brandhorst 2024 showed 2.5-year reduction in biological age after 3 cycles.
Mechanism
Low-calorie, low-protein, low-carb 5-day cycles designed to trigger fasting physiology (ketosis, IGF-1 reduction, autophagy) while allowing some food; monthly cycling
Full Fasting-mimicking diet (FMD / ProLon) review →
Common questions
- Which is better, Extended fasting (24-72h+) or Fasting-mimicking diet (FMD / ProLon)?
- On the composite score, Fasting-mimicking diet (FMD / ProLon) (B-, 6.3/10) edges out Extended fasting (24-72h+) (C, 4.6/10) — but the right pick depends on the specific outcome you're optimising for.
- What's the difference between Extended fasting (24-72h+) and Fasting-mimicking diet (FMD / ProLon)?
- Water-only extended fasting vs a low-calorie diet that mimics it — what trades off in the autophagy/refeeding window.
- Can you take Extended fasting (24-72h+) and Fasting-mimicking diet (FMD / ProLon) together?
- Read Off Label doesn't make stack recommendations — see the disclaimer. Both compounds have individual mechanism, dose, and risk profiles documented on their respective pages; combining them is a clinical question that depends on the goal, indication, and other context.
This is an independent synthesis of published research by a non-clinician.
Comparison-page verdicts use the composite Read Off Label score as a
tiebreaker, but the right pick for any given person depends on indication,
context, and clinician input. See the full
disclaimer and methodology.