Body weight is influenced by the interaction of multiple factors including strong evidence of genetic predisposition to fat accumulation, and obesity tends to run in families. Obesity causes a number of illness such as; diabetes, hypertension, Alzheimer disease… but in general, obese individuals are more likely to die prematurely of degenerative diseases of the heart, arteries, and kidneys, and more importantly, they have increased risk of developing cancer.
How common is obesity?
According to the World Health Organization (WHO), in 2008 about 1.4 billion adults (aged 20 or older) worldwide were overweight and 500 million were obese. Based on WHO data, obesity rates in Europe in 2005 was three times more than what they had been several years earlier. Similar increases were found in the United States, where roughly 15 percent of adults age 20 to 74 were obese in the early 1980s and 34 percent were obese in 2007. The fact remains that, the prevalence of overweight and obesity varied across countries, across towns and cities within countries, and across populations of men and women.
In China and Japan, for instance, the obesity rate for men and women was about 5 percent, but in some cities in China it had climbed to nearly 20 percent. In 2005 it was found that more than 70 percent of Mexican women were obese, and French researchers reported that, worldwide, 40 percent of men and 30 percent of women were overweight and 24 percent of men and 27 percent of women were obese. WHO survey data released in 2010 revealed that more than half of the people living in countries in the Pacific Islands region were overweight, with some 80 percent of women in American Samoa found to be obese.
How does obesity lead to cancer?
- Fat tissue:
- This produces excess amounts of estrogen, it’s high levels have been associated with increased risks of breast, endometrial, ovarian, and some other cancers.
- Increased Levels of Insulin:
- Obese people often have increased blood levels of insulin. This condition, known as hyperinsulinemia precedes the development of type 2 diabetes. Meanwhile, High levels of insulin may promote the development of colon, kidney, prostate, and endometrial cancers.
Other possible mechanisms by which obesity could affect cancer risk include changes in the mechanical properties of the scaffolding that surrounds breast cells and altered immune responses.
- Fat cells:
- Fat cells have also been discovered to have direct and indirect effects on other cell growth regulators, including hormones that may stimulate or inhibit cell growth. For example, the level of an adipokine called leptin, which seems to promote cell proliferation, in the blood increases with increasing body fat. And another adipokine, adiponectin—which is less abundant in obese people than in those of normal weight—may have antiproliferative effects.
- Chronic low-level inflammation:
- More often than not, obese people have chronic low-level inflammation, which can, over time, cause DNA damage that leads to cancer. Overweight and obese individuals are more likely than normal-weight individuals to have conditions or disorders that are linked to or that cause chronic local inflammation and that are risk factors for certain cancers.