User:Murphy18b

Obesity Related Cancers
Obesity is increasing at a frightening rate throughout North America and Europe. It is a known risk factor for diabetes and heart disease but only recently has it become a concern for causing many types of cancers. A recent study in Europe shows that more than 70,000 of the 3.5 million new annually reported cases of cancer are attributed to obesity. An even more recent study performed by the American Cancer Society regarding 900,000 patients with cancer confirmed that obesity was directly associated with an increased rate of death from many types of cancers.

In Australia, obesity is linked to 11% of colon cancers and 9% of post-menopausal breast cancers. More commonly related cancers to obesity are endometrial (39%), esophageal(37%), kidney (25%) and gallbladder (24%). According to studies performed in Australia, the percentages of colon and post-menopausal breast cancers related to obesity are slowly increasing. In the past 15 years, the link between BMI and cancer has increased by 50% in adults and a quarter of the population of children between the ages of 5 and 16 are obese.

In men, obesity was associated with an increased risk of death from stomach and prostate cancers. In women, it was associated with an increased risk of death from post-menopausal breast,cervical, and ovarian cancers. Higher death rates from cancers of the esophagus, rectum, colon, gallbladder, pancreas, and kidney, independently from smoking, were significantly associated with obesity in both men and women. These are referred to as the common cancers. The increased risk for obesity related cancers is most accurately defined in these common cancers. A recent study says that males with a BMI greater than 30 have an 80% increased risk of developing colorectal cancer.

The American Cancer Society says that 14% of all deaths from cancer in men and 20% in women are due to them being overweight or obese. In other words, 90,000 cases of cancer in the United States can be prevented by dieting and increased physical activity. In Europe 9,000 out of 70,000 cases could be prevented all of which are in the United Kingdom.

Obesity of the Abdomen
Five investigators studied 44,000 women with obesity of the abdomen to observe cardiovascular and cancer mortalities. It was observed that the risk of cancer increased by 63% with an increase in waist circumference, even if the women maintained a healthy weight.

Obesity and Breast Cancer
The Long Island Breast Cancer Study Project observed 1,508 women diagnosed with breast cancer in one year. This study observed the effects of weight gain before diagnosis and its association with breast cancer survival. Five years after the diagnosis, 84% of obese women were alive compared to 94% of non-obese women. The study also showed that for every 7 pounds of weight gained after the age of 18 increased the rate of dying from breast cancer by 7%. Women who were pre-menopausal upon diagnosis and didn’t gain more than 35 pounds didn’t have an increased risk of dying from breast cancer but those who gained more than 35 pounds had a twofold-increased risk. Women who were post-menopausal upon diagnosis and gained more than 30 pounds since the age of 50 had a threefold-increased risk of dying from breast cancer.

Association between physical activity and cancer risks
Public health organizations have issued their own guidelines for preventing chronic diseases such as cancer. Specifically they want people to engage in sustained physical activity 5 days a week. This means performing exercises that increase the heart rate for at least 30 minutes each time you exercise. A recent study performed in adults in 48 of the United States provides evidence that obesity is now diet induced rather than a result from lack of physical activity. Only 11 states showed a decrease of physical activity but all 48 showed an increased rate of obesity.

Biological Mechanisms

Increased concentrations of endogenous hormones is a biological mechanism suggested to explain the relation between obesity and increased risk of developing cancer. Endogenous hormones include insulin, insulin growth factor-1(IGF-1), and sex steroids. These hormone levels increase where there is an accumulation of body fat. They are important in growth control of cells, cell differentiation, and cell metabolism. Hyperinsulinemia links obesity related cancer with the high energy, highly processed, carbohydrate and fat diet common in today’s society. Since hyperinsulinemia is common in people with type 2 diabetes, people with type 2 diabetes have an increased risk of obesity related cancers. Hyperinsulinemia results from raised levels of free IGF-1. The environment of the cells is altered so that they favor cancer development. This is more common in men than in women. Chronic inflammation is a contributing factor to the initiation and promotion of cancer cells. Recent studies suggest that obesity is a key component that explains the presence of a chronic, systemic inflammatory response. The presence of this response is associated with an increased risk of colorectal cancer in both men and women. Obesity is linked to the oxidative stress through the inflammatory process. This results in increased oxidative damage to DNA therefore increasing the risk of common cancers.

Medication (added info to section on Obesity page)
Cannabinoids act on two receptors: CB1 and CB2. CB1 receptors are located in the brain and several peripheral tissues. CB2 receptors are mostly found in immune system cells. Cannabinoid receptor antagonists block CB1 receptors which results in decreased food intake. Two of these receptor antagonists are rimonabant and taranabant. Recent clinical studies examining the mechanisms of these receptor antagonists show that the amount of weight lost did not exceed that lost with use of other approved anti-obesity medications. Adverse effects of these CB1 receptor antagonists include potentially severe psychiatric problems which limits their use in the clinic. Orlistat and sibutramine have been available as a prescription for several years but rimonabant has just recently been released in parts of Europe to treat obesity and smoking addiction. CB1 receptor antagonists may reverse the up-regulation of the peripheral cannabinoid system which causes excessive visceral fat accumulation and hyperlipidemia.