Fasting-mimicking diet — The Longevity Fast
The fasting-mimicking diet (FMD) is a periodic, low-calorie, low-protein, high-fat dietary protocol designed to replicate the physiological effects of water fasting while providing essential nutrients. It is highly relevant for longevity as it has been shown to reduce markers of biological aging, lower systemic inflammation, and decrease risk factors for age-related diseases such as diabetes and cardiovascular disease.
Mechanism of Action
The fasting-mimicking diet (FMD) induces a metabolic shift from glucose to fatty acid oxidation and ketogenesis. By restricting calories and specifically limiting protein and sugar intake, the FMD downregulates the nutrient-sensing pathways IGF-1 and mTORC1, while upregulating AMPK. This metabolic state promotes cellular maintenance processes, including autophagy, and reduces systemic inflammation. The periodic nature of the diet allows for a refeeding phase, which is hypothesized to stimulate stem cell-based regeneration and cellular renewal across multiple organ systems.
Human Trial Evidence
Multiple human trials have demonstrated the efficacy of the FMD. A 100-person randomized controlled trial (2017, Science Translational Medicine) showed that 3 cycles of a 5-day FMD reduced body weight, trunk fat, blood pressure, and IGF-1 levels. A subsequent analysis (2024, Nature Communications) indicated that 3 FMD cycles reduced insulin resistance, hepatic fat, and markers of biological age.
Dosing Protocol
5 consecutive days per month for 3-4 months per year. The protocol involves a specific macronutrient ratio: Day 1 provides ~1,100 kcal (11% protein, 46% fat, 43% carbohydrate), and Days 2-5 provide ~725 kcal/day (9% protein, 44% fat, 47% carbohydrate). The diet is plant-based and low in simple sugars.
Safety & Contraindications
Generally safe for healthy adults when used periodically. Adverse effects during the fasting period may include fatigue, headache, dizziness, and hunger. Contraindicated for pregnant or nursing women, individuals with a history of eating disorders, those with a BMI < 18.5, and patients with active infections. Diabetics and individuals on metabolic medications should only undertake the FMD under strict medical supervision due to the risk of hypoglycemia.