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Fasting-Mimicking Diet for Health & Longevity

Created on 10/25/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 5.5 – Audit

The fasting-mimicking diet is a five-day, low-calorie, low-protein, plant-based eating plan, repeated periodically, meant to reproduce the effects of fasting while allowing food. The clearest human evidence concerns modest weight and body-fat loss and better blood sugar control in type 2 diabetes; longer life and tissue regeneration rest mainly on animal work. Tiredness, headache and dizziness are common on diet days, and benefits seem to fade once cycles stop. (Full Review)

Protocol

Standard Prolon regimen
Five consecutive days
Day 1 ≈1,100 kcal, days 2–5 ≈720 kcal of plant-based soups, bars, teas and a supplement
Research schedules
Monthly
Three cycles in generally healthy adults; 12 months alongside primary diabetes care
Maintenance schedule (Longo)
Four times a year
Five-day periods paired with a mostly plant-based, pescatarian everyday diet
Time to effect
Weight and blood pressure
After three cycles
Changes persisted about 3 months after the last cycle in volunteers
HbA1c and liver fat
6–12 months
In type 2 diabetes, gains had generally faded a year after stopping
Ketones and IGF-1
By day 5 of cycle one
Ketones rise and IGF-1 falls

Benefits

Contraindications
  • Pregnant or breastfeeding women
  • People under 18 or over 70 years
  • BMI under 18.5 kg/m²
  • Known, diagnosed or suspected eating disorder
  • Fever, active infection, malnutrition or prior protein deficiency
  • Allergy to nuts, sesame, soy or another diet ingredient
  • Myocardial infarction within the past 6 months
  • Creatinine clearance below 30 mL/min/1.73 m²
  • Heart failure of NYHA class 2 or higher, or LVEF below 40%
  • History of syncope, including with past calorie restriction
  • Diabetes treated with drugs that carry hypoglycemia risk
  • Liver or kidney disorders that low glucose and protein intake could worsen
  • Metabolic disorders impairing glucose production or adaptation to short fasting
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Key Interactions
  • Insulin and sulfonylureas (glipizide, glimepiride): hypoglycemia risk
  • SGLT2 inhibitors (empagliflozin, dapagliflozin): ketoacidosis risk, even with glucose below 250 mg/dL
  • Metformin: falling drug requirement
  • Antihypertensives (lisinopril, losartan): additive pressure lowering, dizziness or fainting (theoretical)
  • Diuretics (furosemide, hydrochlorothiazide): electrolyte imbalance (theoretical)
  • Corticosteroids during chemotherapy (dexamethasone): raised blood glucose, countering the diet's glucose lowering (theoretical)
  • GLP-1 receptor agonists (semaglutide, tirzepatide): may deepen lean-mass loss and nausea (theoretical)
  • Acetaminophen (paracetamol): liver injury at 4–10 g/day associated with recent fasting
  • NSAIDs (ibuprofen, naproxen): may increase stomach irritation (theoretical)
  • Glucose-lowering supplements (berberine, chromium): additive glucose lowering, hypoglycemia (theoretical)
  • Blood-pressure-lowering supplements (magnesium, garlic extract): additive pressure lowering, dizziness (theoretical)
  • Protein and amino acid supplements (whey, leucine): likely blunt the intended growth-signal reductions (theoretical)
  • Alcohol: raises hypoglycemia risk with sulfonylureas and fasting-related acetaminophen liver injury
  • Intense or endurance training: dizziness and impaired performance (theoretical)
    •

Risk & Side Effects

  • High: Transient energy-deficit symptoms
    •
  • Medium:
  • Low: Lean-mass loss; serious adverse events; hypoglycemia with glucose-lowering drugs
    •
  • Speculative: Refeeding-linked tumor promotion; transient immune-cell reduction; triggering disordered eating
    •

Monitoring

Marker Target Why
Fasting glucose 70–99 mg/dL Expected to change; hypoglycemia safety
HbA1c 4.0–5.6% Expected to change in diabetes and prediabetes
Blood pressure Below 120/80 mmHg Expected to change; dizziness safety with blood-pressure drugs
Body weight and waist No established target; change from own baseline Expected to change; undernutrition safety
Lean mass (DEXA) No established target; change from own baseline Safety; a fall changes cycle frequency
IGF-1 No established target; change from own baseline Expected to change
Sodium, potassium and creatinine Sodium 135–145 mmol/L, potassium 3.5–5.0 mmol/L, creatinine about 0.6–1.3 mg/dL, lower in women Electrolyte and kidney-function safety
β-hydroxybutyrate (blood or urine ketones) No established target; a rise during the cycle confirms a fasting-like state Expected to change; safety with SGLT2 inhibitors

Cadence: Baseline before the first cycle; weight, symptoms and (on glucose-lowering drugs) home glucose daily during each cycle; laboratory tests 5–7 days after the third cycle, then every 6–12 months; DEXA every 6–12 months

Qualitative Assessment

  • Energy, hunger and mood on diet days versus refeeding days
  • Dizziness or light-headedness on standing
  • Sleep quality during cycles
  • Exercise capacity and strength between cycles
  • Bowel symptoms in people with inflammatory bowel disease
  • Adherence: number of completed five-day cycles
Not medical advice. Educational distillation of a single evidence review. Confirm any decision with a qualified clinician, especially in the presence of prescription drugs or chronic conditions.