The association between obesity and cancer is looking stronger (see: Risk Factors Relating to the Rising Trend of Hepatocellular Cancer in the U.S.; Why Obese Patients with Cancer Have a Poorer Prognosis). We now learn of research suggesting that obese teenagers have a twofold risk of colorectal cancer by middle age (see: Obese Teenagers Have Twofold Higher Risk for Colorectal Cancer). Below is an excerpt from the article:
Male teenagers who carry a lot of excess weight are more than twice as likely to develop colorectal cancer (CRC) by middle age, according to a large cohort study. Those with a high level of systemic inflammation are also at increased risk. The study...is noteworthy as one of the few to evaluate the association between teenage body mass index (BMI) and bowel cancer in adulthood. It is also the first to evaluate the association of teenage systemic inflammation, assessed here with erythrocyte sedimentation rate (ESR), with this outcome, according to the authors....The investigators analyzed data on BMI and ESR among 239,658 Swedish men who had compulsory military enlistment examinations at 16 to 20 years of age; those with a history of inflammatory bowel disease were excluded...[T]he strong association observed between adolescent obesity and early-to-mid-life CRC, coupled with the increasing prevalence of adolescent obesity...may shed light on the increase in CRC incidence among young adults in the USA," the investigators speculate. Given that the association of BMI with CRC risk was independent of ESR, it may instead be mediated by factors such as insulin, leptin, or steroid hormones, they propose. "However, it is also possible that adolescent BMI may affect CRC through an inflammatory pathway not reflected by ESR," ...[according to the authors].
Here's some interesting information about the causal link between obesity and cancer (see: Obesity And Cancer: You Can Keep Your Weight In Check This Holiday Season):
How obesity increases the risk of cancer is not clear. The American Cancer Society (ACS) suggests it is a complex mechanism that may be related to the immune system and inflammation, as well as insulin, estrogen and other hormones that regulate blood sugar levels, cell division and fat storage. Whatever the reason, the ACS reports the evidence is undisputed about the link between cancer risk, premature death and excess body weight.
It's interesting that that Swedish study cited above also included analysis of the erythrocyte sedimentation rate (ESR) of the obese subjects, a tool, albeit imprecise, for assessing inflammation. Hepatocellular cancer is often proceeded by liver inflammation due to viral infection (see: Risk Factors Relating to the Rising Trend of Hepatocellular Cancer in the U.S.). Here's a brief explanation of the general relationship between inflammation and cancer (see: Why Cancer and Inflammation?):
An association between the development of cancer and inflammation has long-been appreciated. The inflammatory response orchestrates host defenses to microbial infection and mediates tissue repair and regeneration, which may occur due to infectious or non-infectious tissue damage. Epidemiological evidence points to a connection between inflammation and a predisposition for the development of cancer, i.e. long-term inflammation leads to the development of dysplasia. Epidemiologic studies estimate that nearly 15 percent of the worldwide cancer incidence is associated with microbial infection..
Although this discussion is speculative, it provides yet another reason to keep your weight at a recommended level. The risk of diabetes and cardiovascular disease is a more imminent threat from obesity than cancer but the latter also lurks as future complication.
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