Obesity and Risk of Cancer: An Introductory Overview

Abstract

The prevalence of obesity has increased substantially in the past in almost all countries of the world, and a further increase is expected for the future. Besides the well-established effects on type 2 diabetes and cardiovascular disease, there is convincing evidence today that obesity also increases the risk of several types of cancer, including colorectal cancer, postmenopausal breast cancer, endometrial cancer, renal cell carcinoma, esophageal adenocarcinoma, pancreatic cancer, and liver cancer. Obesity probably also increases the risk of ovarian cancer, advanced prostate cancer, gallbladder cancer, and gastric cardia cancer. For some cancer types there is also some evidence that weight gain during adulthood increases cancer risk, e.g., colorectal cancer, postmenopausal breast cancer, endometrial cancer, and liver cancer. However, for most cancers it is an open question as to whether vulnerability to weight gain in relation to cancer risk depends on specific life periods. There are a number of plausible mechanisms that may explain the relationship between obesity and cancer risk, including pathways related to insulin resistance, inflammation, and sex hormones. For most cancers there is only limited evidence that weight loss in adulthood decreases cancer risk, which is primarily due to the limited long-term success of weight loss strategies among obese individuals.There is limited evidence suggesting that obesity may also be associated with poor prognosis among patients with colorectal cancer, breast cancer, endometrial cancer, ovarian cancer and pancreatic cancer. Taken together, these findings support efforts to prevent weight gain on an individual level as well as on a population level. Whether and to what extent overweight or obese cancer patients benefit from weight loss strategies is unclear and a matter of debate.

Body fatness at a young age, body fatness gain and risk of breast cancer: systematic review and meta‐analysis of cohort studies

“…Notably, although the current findings indicate that a higher body fatness at a young age appears to be protective against the risk of breast cancer later in life, being overweight or obese during this period of life is not advocated because the potential detrimental role of excess body fatness in the development of chronic diseases, certain types of cancer and other health conditions far outweighs its potential protective role on breast cancer. Age is regarded as a well‐established risk factor for breast cancer because the incidence rates of breast cancer increase with age .…”

“…The connection between body fatness/adiposity and breast cancer throughout the life course is complex. In this meta‐analysis, the inverse association between higher body fatness at a young age and the risk of postmenopausal breast cancer is somewhat surprising because various measures of adiposity (BMI at cohort entry, weight gain, waist circumference and waist‐to‐hip ratio) have been largely linked to a higher risk of developing this malignancy after menopause . It is almost impossible to isolate a single factor that is fully responsible for the development of breast cancer.…”

“…Excess body fatness in adulthood has been consistently associated with an increased risk of postmenopausal breast cancer and a trend towards a lower risk of premenopausal breast cancer . By comparison, we found that higher body fatness at a young age was associated with a lower risk of breast cancer in both premenopausal and postmenopausal women.…”

Multiple primary cancers associated with endometrial and ovarian cancers: An analysis based upon the Japan Autopsy Annual Database from 2002 to 2010

“…Therefore, patients with rapidly progressing gallbladder and bile duct cancers have a lesser chance of developing other cancers. Previous studies reported that colorectal, endometrial and breast cancers have common exogenous risk factors such as obesity/body weight gain and dietary habit . Obesity is strongly associated with endometrial cancer, but is weakly associated with postmenopausal breast cancer and colon cancer .…”

Assessment of Awareness Levels toward Colorectal Cancer Early Detection and Prevention in Saudi Arabia

“…Plausible biological mechanisms include insulin resistance, hyperinsulinemia, chronic inflammation, altered levels of growth factors, adipocytokines and steroid hormones. In addition to its effect on colorectal cancer incidence, obesity may play a role in colorectal cancer recurrence, treatment outcomes and survival [20,21]. The adipokines adiponectin and leptin and adipocytemediated chronic low-grade inflammation represented by the acute-phase C-reactive protein may explain a substantial part of the association between obesity and risk of colorectal cancer [22].…”