What Is The Relationship Between Obesity, Physical Inactivity and Cancer Risk?

What Is The Relationship Between Obesity, Physical Inactivity and Cancer Risk?

Let’s discuss the relationship between physical activity and cancer risk. This is not something you hear discussed very often but there is mounting evidence linking the two. It’s worth taking a few minutes to discuss and learn more about that relationship.

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What Is The Relationship Between Obesity, Physical Inactivity and Cancer Risk?

The number of cancer cases caused by being obese is estimated to be as high as 20%. That fact alone is astounding and the data supports it. The risk of malignant cancer appears to be influenced by physical activity, body fat, diet and weight fluctuations.

That following types of cancer have strong evidence to a link with obesity as possible cause: endometrial, esophageal adenocarcinoma, colorectal, postmenopausal breast, prostate, pancreas, kidney, and thyroid.

The evidence is less definitive but expanding for the relationship between obesity and a number of other cancers including leukemia, non-Hodgkin's lymphoma, multiple myeloma, malignant melanoma, ovarian, and liver.

Because of cigarette and tobacco use, the association between obesity and lung, head and neck cancer is not as clear.

Researchers have begun to shift their attention towards folks who have poor health profiles that include being overweight or obese, lacking physical activity and generally poor diets. Studying all these factors will help researchers and physicians better understand the relationship between each and the risk of cancer.

Many biological mechanisms have been proposed as related to obesity and cancer and are currently being investigated. The best evidence includes changes in

  • sex hormones (estrogen, testosterone, etc)
  • Insulin
  • Insulin like growth factor 1
  • adipokines (signaling hormones released from fat cells)

Other proposed mechanisms which require more research

  • inflammation (chronic)
  • oxidative stress
  • immune dysfunction
  • other growth factors
  • obesity induced hypoxia
  • genetic susceptibility

The evidence also suggests that certain races or ethnic subgroups are at increased risk for certain diseases. For example, according to the CDC in 2010, the risk of all types of cancer was highest in white women (409.9/100,000) and highest in black men (553.2/100,000). The relationship of obesity to cancer and race is currently being investigated.

So then, what is the relationship between physical activity and cancer survivership?

After a diagnosis of breast cancer, physical activity may improve quality of life, reduce fatigue and assist with energy balance according to a few studies.

Another study found that women who exercised moderately after a diagnosis of breast cancer had improved survival rates compared with more sedentary women.

Although promising research is occurring, it’s too early to draw any definitive conclusions about breast cancer survival and physical activity.

In two studies looking at men diagnosed with colon cancer, the authors found participants with higher levels of physical activity post-diagnosis were less likely to have a cancer recurrence and had increased survival. Interestingly, activity levels prior to diagnosis were not related to survival.

Can physical activity prevent cancer?

Because we know that people who don’t exercise are at increased risk of developing cancer, it stands to reason that people who do exercise may be reducing their risk.

According to the national cancer institute, studies have shown people who exercise regularly have a reduced risk of developing colon cancer, breast cancer, uterine and lung cancer.

Prevention appears to occur for many of the same reasons that risk is increased in those who do not exercise: physical activity helps the body properly regulate sex hormones, Insulin, Insulin like growth factor 1, adipokines and many of the other factors I mentioned earlier.

There is a collaborative effort going on right now to fully investigate the relationship between physical activity and cancer. (Called Transdisciplinary Research on Energetics and Cancer through the National Cancer Institute)

So how much exercise do you need?

The Centers for Disease Control and Prevention (CDC) recommend that adults “engage in moderate-intensity physical activity for at least 30 minutes on five or more days of the week,” or “engage in vigorous-intensity physical activity for at least 20 minutes on three or more days of the week”.

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