The World Cancer Research Fund estimates that about 20% of all cancers diagnosed in the US are related to body fatness, physical inactivity, excess alcohol consumption, and/or poor nutrition, and thus could be prevented (2015). Although all of those factors are related and may contribute to cancer risk, but the one which has the strongest evidence that links with cancer is body weight. Cancer is an deviant growth of cells caused by multiple changes in gene expression leading to unbalance of cell proliferation and cell death and ultimately evolving into a population of cells that can invade tissues and metastasize to distant sites, causing significant morbidity and, if untreated, death of the body. There are a lot of cancers that associate with overweight and obesity, as you can see from figure 1 that being overweight or obese is clearly linked with the increase risk of many type of cancers. This may include cancers such as breast cancer (postmenopausal), liver cancer, kidney cancer and much more. According to the American Cancer Association, what leads a higher risk of those types of cancer are usually because of having too much belly fat (having a larger waistline).
The timing of weight gain could also affect cancer risk. The older you get, the higher risk to gain cancer. There are also theories that state losing weight could reduce cancer risk, but there are only limited cancers’ percentage rate that could be reduced from losing weight. This varies from breast cancer (postmenopausal), more aggressive forms of prostate cancer, and possibly other cancers as well (NCI Website). For a relationship between weight loss and cancer risk, there are stronger evidence which comes from studies of people who went through bariatric surgery. Bariatric surgery is a surgery that is performed on the stomach or intestines to induce weight loss (NCI Website). When obese people take the bariatric surgery, they appear to have lower risks of obesity-related cancer than those who have not undergone bariatric surgery (Tee et al.). Even when obese people don’t take the bariatric surgery, losing weight is always encouraged. Evidence shows that obese people who intentionally lose weight have reduced levels of certain hormones that are related to cancer risk such as insulin, estrogens, and androgens (ACA Website). Losing weight could also affect many other health benefits for example lowering the risk of heart disease and diabetes.
The increase of obesity to cancer is also due to the increase of mitosis rate. With obesity, the excess body weight inevitably leads to an increase of joint deterioration and arthroses in the knee and hip joints. The injury to intervertebral disks is seen more frequently as well (Munsch 54). There is a correlation between increased food ingestion leading to an increased cell metabolism. However, due to that correlation, it is also seen the more mitosis rates increased, the more errors it could result in mitosis. Therefore, with excessive food ingestion – obesity is always a consequence of increased food ingestion – the incidence of cancer also increases (Munsch 54). Specific cancer rates may appear differently for each gender. In women, the risk is usually increased for endometrial cervical, and ovarian cancer, as well as for post-menopausal breast cancer (Munsch 54). While in men, intestinal and prostate cancers usually has a higher risk (Munsch 54). The risk of dying of cancer is increased by about 55% in adipose (used for the storage of fat) women and about 33% in adipose men (Munsch 54). Based on figure 2, an overview on how obesity affects getting a higher cancer risk, pancreas also affect a higher change in cancer risk. As well as the immune system and adipose tissue, all three causes are important factors on the relation between obesity and cancer.
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“Does Body Weight Affect Cancer Risk?” American Cancer Society, 24 Apr. 2015, www.cancer.org/cancer/cancer-causes/diet-physical-activity/body-weight-and-cancer- risk/effects.html.
Kazan M, Karalti I? (2015) The Association between Obesity and Cancer. Endocrinol Metab Syndr 4: 196. doi:10.4172/2161-1017.1000196
Munsch, Simone. Obesity and Binge Eating Disorder. Karger, 2005.
“Obesity and Cancer.” National Cancer Institute, 17 Jan. 2017, www.cancer.gov/about-cancer/ causes-prevention/risk/obesity/obesity-fact-sheet#q8.
Tee, M C, et al. “Effect of Bariatric Surgery on Oncologic Outcomes: a Systematic Review and Meta-Analysis.” Surgical Endoscopy., U.S. National Library of Medicine, Dec. 2013, www.ncbi.nlm.nih.gov/pubmed/23949484.
“Vital Signs.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 3 Oct. 2017, www.cdc.gov/vitalsigns/obesity-cancer/ infographic.html#graphic.