The feasibility and safety of fasting-mimicking diet in breast cancer patients with chemotherapy in China.

Purpose: The Fasting-Mimicking Diet (FMD) has emerged as a promising approach for mitigating the side effects and enhancing the efficacy of chemotherapy in cancer patients, while it is still challenging to implement FMD in clinical setting due the concern of nutritional supplements. This study is aimed to evaluate the feasibility of a recipe-based FMD among breast cancer (BC) patients, and assessing its effects on metabolic health and body composition.

Methods: This is a single-arm, pilot clinical trial involving BC patients undergoing chemotherapy. Participants were required to adhere to the FMD recipes for four days prior to and on the day of each chemotherapy cycle, which provided 34-54% of the normal caloric intake, with a total of three cycles needed for the study. FMD-related adverse events, body composition, and serum samples were monitored.

Results: A total of 30 participants were enrolled, and 27 of them completed 3 cycles of the FMD. The incidence of grade III or worse FMD-related adverse effects was 5.95% (5/84). A decline in IGF-1 compared to baseline was observed to be statistically significant at the end of the first FMD (B =  - 23.29, p = 0.001) and second FMD (B =  - 16.20, p = 0.023), but no statistical difference at the end of the third FMD (B =  - 8.372, p = 0.327). After 3 FMD cycles and a 21-day washout, BC patients experienced a statistically significant reduction in body mass (- 2.04kg, 95% CI - 2.86, - 1.21 kg; p < 0.001), fat mass (- 1.88kg, 95% CI - 2.72, - 1.05 kg, p < 0.001), visceral fat area (- 14.78%, 95% CI - 21.13, - 8.43%, p < 0.001) and waist circumference (- 4.01,95% CI - 6.18, - 1.83, p < 0.001), while muscle mass remained stable (- 0.05 kg, 95% CI - 0.36, 0.27 kg; p = 0.270).

Conclusion: The recipe-based FMD program is well-tolerated by BC patients. It is proved to be safe, with few or no fasting-related adverse effects and an acceptable magnitude of weight loss. Additionally, it is effective in reducing IGF1, indirectly correlating to insulin resistance and inflammation that could enhance efficacy of anticancer therapies.