Fasting-Based Dietary Interventions in Cancer Patients and Survivors: A Scoping Review

Background: Fasting-based interventions are increasingly investigated as adjuncts to cancer treatment for the potential to reduce therapy-related toxicities, improve metabolic health, and enhance quality of life. However, clinical evidence regarding their efficacy, tolerability, and acceptability remains limited and fragmented. This scoping review aimed to systematically map the current evidence on fasting-based interventions in cancer patients and survivors. Methods: A literature search was conducted in PubMed, Scopus, Web of Science, and CINAHL up to 10 June 2025. Eligible interventional studies included cancer patients or survivors and evaluated fasting-based interventions, such as time-restricted eating, intermittent fasting, short-term fasting, or fasting-mimicking diets. Studies were categorized by fasting types and outcomes like fatigue, treatment toxicity, metabolic and hematologic parameters, weight, quality of life, adherence, acceptability, illness perception, and adverse events were assessed. Result: Twenty interventional studies of FMD, TRE, STF, IF, or fasting combined with altered dietary approaches conducted across 10 countries were included, comprising a total of 871 participants. Participant ages ranged from 28 to 75 years. Overall, 9 of 20 studies exclusively enrolled breast cancer patients or survivors, and chemotherapy was the most common treatment context in 11 studies. Five of six studies reported reductions in fatigue. Among the five studies assessing quality of life, one demonstrated improvement, three reported no change, and one yielded mixed results. Six of eight studies reported reductions in chemotherapy-related toxicity, and weight loss was observed in 10 of 12 studies. Reductions in IGF-1 and insulin levels were reported in six of seven and four of five studies, respectively. Hematologic changes were noted in six studies, and only one study assessed illness perceptions, reporting positive findings. Fasting-related adverse events, reported in nine studies, were generally mild and transient. High adherence and acceptability were observed across studies; however, findings were heterogeneous across intervention types and were largely derived from small or moderate-strength studies. A descriptive quality metric assessment indicated that most studies were of moderate methodological strength. More intensive fasting protocols, such as FMD and STF, appeared to demonstrate more consistent metabolic effects, whereas TRE showed higher adherence but more variable clinical outcomes. Conclusions: Fasting-based interventions have the potential to be feasible and well tolerated among cancer patients and survivors, with early evidence suggesting benefits in reducing fatigue, minimizing treatment-related toxicities, and favorable metabolic effects. Large, well-designed trials including diverse cancer populations are needed to confirm long-term outcomes and guide clinical integration.