Gastrointestinal cancer and obesity

Growing evidence has associated the gut microbiota with the onset of inflammation, a common feature of both obesity and cancer. Here, Cani and Jordan review the links between the gut microbiota, metabolic disorders and the development of gastrointestinal cancer.

Excess adiposity is a risk factor for many cancers of the gastrointestinal system. In this Review, the authors examine the epidemiological evidence of associations between obesity and gastrointestinal cancer risk and explore the potential mechanisms underlying these relationships.

Intervention studies have helped characterize the potential mechanisms linking obesity and risk of gastrointestinal cancers in humans. Here, the authors explore the findings of these trials and detail how the key pathways involved, including inflammation, adipokines and metabolic dysfunction, might modulate carcinogenesis in gastrointestinal tissues.

An association between obesity and many cancers exists, but how obesity affects the tumour microenvironment remains poorly understood. This Review explores key pathways linking visceral obesity and gastrointestinal cancer, including inflammation, hypoxia, stromal and immune cell function, metabolism and angiogenesis.

Bariatric surgery-induced weight loss is associated with reduced overall cancer incidence; however, some data suggest that risk of colorectal cancer (CRC) actually increases. Here, we suggest a need to fully characterise CRC (and colorectal adenoma) risk after bariatric surgery given that preventive measures (early diagnosis and polypectomy) can mitigate risk.

Obesity is an established risk factor for gastrointestinal cancers. Interventions that reduce the burden of obesity at both the societal and individual level and targeted interventions among those at higher risk of cancer should be developed, supported by advances in understanding of the biology that underpins the obesity–cancer link.