Fasting Mimicking Diet for Metabolic Syndrome: A Narrative Review of Human Studies

Metabolic syndrome (MetS) is an association of risk factors that share insulin resistance (IR), exerting a super cumulative effect on the risk of developing cardiometabolic diseases. Lifestyle optimization is a key element in the prevention and non-pharmacological therapy of MetS. Certain studies have concluded that some dietary patterns could be more beneficial as an adjunctive treatment for MetS. Fasting mimicking diet (FMD) is a form of periodic fasting in which caloric intake is restricted for 5 days each month. It has been studied for its beneficial effects not only in patients with neoplasia and neurodegenerative diseases but also for its effects on IR and metabolism. In this narrative review, the effects of FMD in patients with MetS were analyzed, focusing on its impact on key metabolic components and summarizing findings from human studies. FMD has demonstrated beneficial effects on MetS by reducing BMI and waist circumference, preserving lean mass, and improving the metabolic profile. Moreover, individuals with a higher BMI or a greater number of MetS components appear to derive greater benefits from this intervention. However, limitations such as high dropout rates, small sample sizes, and methodological constraints restrict the generalizability of current findings. Further large-scale studies are needed to confirm these effects and establish FMD as a viable non-pharmacological strategy for managing MetS.