Can you take Extended fasting (24-72h+) and Fasting-mimicking diet (FMD / ProLon) together?

The available evidence is use- and population-specific. Each page documents mechanism, studied or reported dose context, risks, and legal status; the database does not determine whether a combination is appropriate for an individual.

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

Score comparison

Fasting-mimicking diet (FMD / ProLon) has the higher descriptive composite (B-, 6.3/10) compared with Extended fasting (24-72h+) (C, 4.6/10). The axes below show whether that difference comes from evidence, reported benefit, safety, or a combination.

Extended fasting (24-72h+)

C 4.6/10

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 / route context: Reported protocols include periodic 24-72h fasts sometimes repeated quarterly to annually; electrolyte and refeeding considerations vary with duration and individual context
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).

Studied, labeled, or reported-use context: Reported protocols include periodic 24-72h fasts sometimes repeated quarterly to annually; electrolyte… — N/A; not individualized guidance.

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 →

Fasting-mimicking diet (FMD / ProLon)

B- 6.3/10

Evidence: Moderate (6/10)
Benefit: Med (5/10)
Risk: Low-Med (7/10 safety)
Legality: Commercial (ProLon) or DIY
Dose / route context: 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.

Studied, labeled, or reported-use context: 5 days monthly; ~1100 kcal day 1, ~750 kcal days 2-5; very low protein/carb — Commercial (ProLon) or DIY; not individualized guidance.

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

How do the evidence profiles of Extended fasting (24-72h+) and Fasting-mimicking diet (FMD / ProLon) compare?: Fasting-mimicking diet (FMD / ProLon) has the higher descriptive composite (B-, 6.3/10) compared with Extended fasting (24-72h+) (C, 4.6/10). The axes below show whether that difference comes from evidence, reported benefit, safety, or a combination.
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?: The available evidence is use- and population-specific. Each page documents mechanism, studied or reported dose context, risks, and legal status; the database does not determine whether a combination is appropriate for an individual.

This is an independent synthesis of published research by a non-clinician. The comparison reports composite and axis-level differences without selecting an intervention for the reader. Relevance depends on indication, population, dose, duration, and other context. See the full disclaimer and methodology.