Fasting-Mimicking Diet (FMD)

What it is

The Fasting-Mimicking Diet, developed by Valter Longo, is a 5-day low-calorie regimen (~1100 kcal day 1, ~750 kcal days 2–5) with very low protein, low sugar, and modest fat from specific plant sources. Marketed commercially as ProLon. Typically repeated monthly or quarterly.

Rationale

Standard caloric restriction is hard to sustain. Periodic short fasts trigger many of the same cellular programs (autophagy, mTORC1 suppression, ketogenesis) and may rejuvenate immune cell populations through cycles of depletion and re-expansion.

What the human evidence shows

In the Wei et al. 2017 RCT, three monthly FMD cycles in adults reduced:

• Body weight, body fat, waist circumference (modest, ~3%).
• Systolic blood pressure.
• IGF-1 and fasting glucose in those with baseline elevations.
• C-reactive protein in elevated-baseline subjects.

Subsequent trials suggest possible benefits for chemotherapy tolerance and multiple sclerosis biomarkers.

Practical considerations

• Requires planning and provisions (commercial ProLon is convenient; DIY is possible with the published macronutrient framework).
• Most people can do 5 days; first cycle is hardest.
• Avoid during pregnancy, in low-BMI individuals, on insulin/sulfonylureas without supervision, in eating-disorder history, in significant frailty.
• Not a daily diet; benefits come from periodic cycles.

Related entries

Caloric restriction, Intermittent fasting, Valter Longo.