Fasting-Mimicking Diet Proves Safe for Chinese Breast Cancer Patients on Chemo

Breast cancer is the second most common cancer in Chinese women, with chemotherapy playing a central role in treatment. However, chemo is associated with weight gain, increased body fat, metabolic dysfunction, and reduced quality of life—all of which independently worsen prognosis. The fasting-mimicking diet (FMD), developed by Prof. Valter Longo, is a short-term, plant-based, low-calorie dietary protocol hypothesized to protect healthy cells while sensitizing tumor cells to chemotherapy through differential stress resistance (DSR) and IGF-1/mTOR pathway modulation.

This single-arm pilot trial at Ruijin Hospital, Shanghai, enrolled 30 female breast cancer patients (mean age 42, mean BMI 22.8) receiving EC or TC chemotherapy regimens. A Chinese multidisciplinary team adapted the FMD into a recipe-based format using familiar local foods rather than Western meal-replacement products. Patients followed the 5-day FMD (days −4 through chemo day) for three consecutive chemotherapy cycles, consuming roughly 50% of normal calories on day one and ~34% on days two through five, with macros weighted toward plant fats (44–56%), moderate carbohydrates (34–47%), and low protein (9–10%). Between cycles, normal eating resumed.

Twenty-seven of 30 participants (90%) completed all three FMD cycles. Grade III or worse adverse events occurred in only 5.95% of FMD exposures (5 of 84 cycle-completions), well below the prespecified safety threshold. Common milder complaints included fatigue, dizziness, and headache, consistent with known fasting-related effects. Adherence to the prescribed recipes was high, monitored via daily food logs and WeChat check-ins with specialized nurses.

Metabolic effects were meaningful. IGF-1 levels fell significantly from baseline at the end of FMD cycle one (B = −23.29, p = 0.001) and cycle two (B = −16.20, p = 0.023), though the effect attenuated by cycle three (B = −8.37, p = 0.327), possibly reflecting adaptation. After three cycles and a 21-day washout, patients showed significant reductions in body mass (−2.04 kg), fat mass (−1.88 kg), visceral fat area (−14.78%), and waist circumference (−4.01 cm), while skeletal muscle mass remained stable (−0.05 kg, p = 0.270). Lipid and protein markers were also tracked post-cycle.

These findings are important for several reasons. First, they establish proof-of-concept that a culturally adapted, food-based FMD—not requiring imported meal-replacement kits—is feasible in a population with strong traditional food beliefs. Second, the muscle-sparing fat loss profile is clinically desirable, as chemotherapy-associated sarcopenia is a known risk. Third, IGF-1 reduction is mechanistically linked to improved cancer cell chemosensitivity, suggesting the diet may augment treatment efficacy. The trial lays groundwork for a larger randomized controlled trial with tumor response endpoints.