Associations among physical activity, diet, non-lifestyle characteristics and the gut microbiome of cancer patients: A scoping review and network analysis

Lifestyle factors, such as physical activity and dietary modifications can beneficially modulate the gut microbiome of cancer patients, however their effects are often shaped by non-modifiable variables. This review and network analysis aims to synthesize current evidence on how both lifestyle and non-lifestyle factors affect the gut microbiome in cancer patients. A systematic search was conducted on Scopus, CINAHL, PubMed and Web of Science to produce 51 eligible studies for this review. A chi-square test of independence indicated that the distribution of gut bacteria function categories was significantly associated with the category of influencing factor (Χ² = 390.87, p = 0.032). Across studies, high physical activity and healthy diets were associated with increased abundances of saccharolytic/short-chain fatty acids and lactic acid-producing bacteria, alongside decreased abundances of pathogenic or opportunistic bacteria. However, these associations may also be influenced by non-lifestyle characteristics such as chemotherapy, age, and cancer type or stage which could mask the benefits of lifestyle interventions. This study highlights the limited but growing evidence linking physical activity, diet and the gut microbiome in cancer populations. Progress in this field will require larger, more integrative designs that account for non-lifestyle confounders and apply advanced analytical approaches to capture complex interactions.