Obesity and Colorectal Cancer

Abstract

Obesity is a risk factor for colorectal cancer based on its molecular and metabolic effects on insulin and IGF-1, leptin, adipocytokines, and sex hormones. Obese men have a higher risk of colorectal cancer compared with normal weight men, but the association between obesity and rectal cancer is weaker than with colon cancer. There is a weaker association between obesity and colon cancer in women than in men, and no appreciable association between obesity and rectal cancer in women. Although obesity does not seem to have an effect on the number of lymph nodes harvested with resection, obesity does seem to be associated with more-aggressive colorectal cancers in a handful of studies. Survival and local recurrence studies are contradictory with no conclusive evidence that obesity predisposes to worse overall survival or increased recurrence in colon and rectal cancers. The literature is not definitive as far as overall morbidity and mortality rates in the obese are concerned, though obese rectal cancer patients seem to incur proportionally more morbidity and mortality. Preexisting steatosis or steatohepatitis in obese colorectal cancer patients or chemotherapy-induced liver dysfunction may lead to an increased mortality in obese patients with colorectal liver metastases. Diabetes may cause poorer response to neoadjuvant therapy in rectal cancer and contribute to higher mortality and recurrence in colon cancer.

Colorectal cancer in the world: incidence, mortality and risk factors

“…Daily inactivity can increase the incidence of obesity, which is another risk factor for CRC (Bardou et al, 2013). The precise mechanism of the protective effect of physical activity is still unclear, but it seems that physical activity lowers the risk of CRC by reducing BMI, reducing the colonic transit time, and lowering insulin levels (Gribovskaja-Rupp et al, 2011;Mao et al, 2003). Obesity increases serum leptin levels (Frezza et al, 2006); leptin leads to CRC development (Sierra-Honigmann et al, 1998).…”

Association of obesity and overweight with overall survival in colorectal cancer patients: a meta-analysis of 29 studies

“…Excessive fat accumulation, including overweight and obesity, defined as a body mass index (BMI) of 25-29.9 and C30 kg/m 2 , respectively, according to the World Health Organization (WHO), has emerged as an important lifestyle-related factor for the development of CRC [7,8]. The relationship between obesity and CRC incidence has been extensively investigated.…”

“…There is no conclusive evidence that obesity predisposes to poorer survival in CRC patients [6,8,9]. For example, a US cohort study of 2,303 non-metastatic CRC patients showed that pre-diagnostic obesity was significantly associated with an increased risk of death resulting from all causes and from CRC [11].…”

A DASH dietary pattern and the risk of colorectal cancer in Canadian adults

“…Insulin and insulin-like growth factor 1 together can promote CRC by activating several signalling pathways associated with an elevated risk of oncogenesis. 32 That insulin may play a role in the development of CRC is supported by the association between type 2 diabetes and an elevated risk of cancer including CRC. 33,34 Since the Mediterranean and DASH diets are very similar (e.g.…”