Obesity and cancer

2 out of every 3 Americans will have a cancer diagnosis in their lifetime – that means every single American will be impacted in some way by cancer.

Being overweight brings with it an increased risk of cancer. In fact, obesity causes around three million cancer deaths every year worldwide.

Key Points About Obesity and Cancer

During the past several decades, the percentage of overweight and obese adults and children has increased markedly.

Obesity is associated with increased risks of cancers of the esophagus, breast (postmenopausal), endometrial (the lining of the uterus), prostate, colon and rectum, kidney, pancreas, thyroid, gallbladder, and possibly other cancer types.

Obese people are also at higher risk of coronary heart disease, stroke, high blood pressure, diabetes, and a number of other chronic diseases.

Data from observational studies have shown that people who have a lower weight gain during adulthood have a lower risk of:

Colon cancer
Breast cancer (after menopause)
Endometrial cancer
Prostate cancer

A more limited number of observational studies have examined the relationship between weight loss and cancer risk, and have found decreased risks of breast cancer, prostate and colon cancer among people who have lost weight.

It is important to note that whereas most lifestyle weight loss interventions result in weight losses of 7-10 percent of body weight unless combined with lifestyle changes that generally results in weight loss of up to 30 percent.

One study estimated that in 2007 in the United States, about 34,000 new cases of cancer in men (4 percent) and 50,500 in women (7 percent) were due to obesity. The percentage of cases attributed to obesity varied widely for different cancer types but was as high as 40 percent for some cancers.

A projection of the future health and economic burden of obesity in 2030 estimated that continuation of existing trends in obesity will lead to about 500,000 additional cases of cancer in the United States by 2030.

Several possible mechanisms have been suggested to explain the association of obesity with increased risk of certain cancers:

Fat tissue produces excess amounts of estrogen, high levels of which have been associated with the risk of breast, endometrial, and some other cancers.

Obese people often have increased levels insulin in their blood, which may promote the development of certain tumors.

Fat cells produce hormones, which may stimulate or inhibit cell growth. For example, lepton, which is more abundant in obese people, seems to promote cell proliferation.

Fat cells may also have direct and indirect effects on other tumor growth.

Obese people often have chronic low-level inflammation, which has been associated with increased cancer risk.

Most research has concentrated on the link between obesity and breast cancer, as scientists think that fat cells produce estrogen, which is a key factor in causing this kind of cancer. Research is also examining the effect of obesity on cancer in men, and a new study has shown that being overweight means men are more likely to develop prostate cancer.

When you are overweight, you don’t just put on weight in the obvious places such as your hips, thighs, arms and around your waist. Lots of the fat is also deposited around and in your vital organs.

What researchers have done is analyze fat surrounding the prostates of men who were undergoing surgery for prostate problems. They studied medical conditions such as the increase in prostate size – and prostate cancer confined to the gland. Researchers also looked at men whose cancers had spread to other organs. The men were divided into two groups, lean or obese, depending on whether their body mass index was higher or lower than 25. When the results were analyzed the fat around the prostate was found to be different between the lean and obese men. Irrespective of whether the men had benign or malignant prostatic disease, the fat around the prostates of the obese men was different. The difference was that there was more gene activity in the obese men. This included some very important genes, which can affect many aspects of immune strength and which are involved in inflammation. Crucially, it included genes, which affect cell growth and proliferation and programmed cell death. More and more genes came into play as cells transformed from harmless to cancerous. So activity increased between benign tumors and prostate cancer, and between cancer confined to the prostate and cancer that had spread to other parts of the body. As the cancer progressed there was a gradual increase in disorderly gene behavior. The more you are overweight, the more disorderly the genes.

The lead investigator was in no doubt about how men should interpret his findings and the action they should take. He said: “In an increasingly obese population, understanding how fat, especially fat surrounding the prostate can influence the growth and severity of prostate cancer may provide an opportunity for implementing personalized lifestyle changes and treatment strategies.”

If you want to decrease the odds of being diagnosed with cancer the message is simple – stay lean