Domain-specific physical activity and sedentary behaviour in relation to colon and rectal cancer risk: a systematic review and meta-analysis

White adipose tissue was believed to be just an energy-storage organ, but it is now recognized to be an active participant in energy homoeostasis and physiological functions such as immunity and inflammation. Macrophages are components of adipose tissue and actively participate in its activities. Adipose tissue is known to express and secrete a variety of products known as 'adipokines', including leptin, adiponectin, resistin and visfatin, as well as cytokines and chemokines such as tumor necrosis factor-alpha, interleukin-6 and monocyte chemoattractant protein-1. The release of adipokines by either adipocytes or adipose tissue-infiltrated macrophages leads to a chronic subinflammatory state that could play a central role in the development of insulin resistance and type 2 diabetes, and the increased risk of cardiovascular disease associated with obesity.

To determine whether physical inactivity and obesity increase risk for colon cancer and adenomas, which are precursors of cancer, and whether the abdominal distribution of obesity is an independent risk factor for these events. Prospective cohort study. United States. 47,723 male health professionals, 40 to 75 years of age, who responded to a questionnaire mailed in 1986. Questionnaires in 1986 about physical activity level and body mass index, and questionnaires in 1987 (31,055 respondents) about waist and hip circumferences. Between 1986 and 1992, 203 new patients were diagnosed with colon cancer and 586 were diagnosed with adenomas. Physical activity was inversely associated with risk for colon cancer (high compared with low quintiles of average energy expenditure from leisure-time activities: relative risk, 0.53 [95% CI, 0.32 to 0.88], P for trend = 0.03) after adjustment for age; history of colorectal polyp; previous endoscopy; parental history of colorectal cancer; smoking; body mass; use of aspirin; and intake of red meat, dietary fiber, folate, and alcohol. Body mass index was directly associated with risk for colon cancer independently of physical activity level. Waist circumference and waist-to-hip ratio were strong risk factors for colon cancer (waist-to-hip ratio > or = 0.99 compared with waist-to-hip ratio or = 43 inches compared with waist circumference or = 73 inches compared with height < or = 68 inches: multivariate relative risk, 1.76 [CI, 1.13 to 2.74], P for trend = 0.02). The results support an inverse association between physical activity and risk for colon cancer, whereas height and obesity, particularly abdominal adiposity, are associated with an elevated risk.

To determine whether interrupting prolonged sitting with brief bouts of light-intensity walking (LW) or simple resistance activities (SRA) improves postprandial cardiometabolic risk markers in adults with type 2 diabetes (T2D).