Weight Gain, Obesity & Cancer Risk

Excess weight is a known risk factor for many chronic diseases, such as diabetes and heart disease. Obesity can also be linked an increased risk for developing some cancers. To clarify the effects of weight gain on cancer risk, researchers in 2007 conducted an analysis of many studies reported in medical journals that describe 282,137 cases of cancer. The researchers wanted to see if weight gain had an effect on the risk for certain cancer types.

In particular, the researchers looked at the risk of cancer associated with a weight gain corresponding to an increase of 5 kg/m² in body mass index (BMI). In terms of actual pounds gained, a man with a normal-range BMI of 23 would need to gain 15 kg (33 lbs.) of weight, while a woman with a BMI of 23 would need to gain 13 kg (28.6 lbs.) to correspond to an increase of 5 in the BMI.

The results, published in the Lancet in February 2008, revealed that weight gain is positively associated with the risk of developing a variety of types of cancer as described below.

For women, a weight gain corresponding to an increase of 5 in the BMI resulted in a significant increase in risk for developing four cancer types:

• esophageal adenocarcinoma (double the risk),
• endometrial cancer (slightly more than double the risk),
• gallbladder cancer (slightly more than double the risk), and
• kidney (renal) cancer.

In women, a weaker but still positive increase in cancer risk with weight gain was demonstrated for the following cancer types:

• postmenopausal breast cancer,
• pancreatic cancer,
• thyroid cancer,
• colon cancer,
• leukemia,
• multiple myeloma, and
• non-Hodgkin's lymphoma.

Significant increases in cancer risk associated with weight gain in men were observed for the following cancers:

• esophageal adenocarcinoma (double the risk),
• thyroid cancer,
• colon cancer, and
• renal cancer.

Additionally, weaker but still positive associations between cancer risk and weight gain in men were noted for

• rectal cancer,
• malignant melanoma,
• leukemia,
• multiple myeloma, and
• non-Hodgkin's lymphoma.

While the researchers explain that the exact mechanisms by which weight gain increases cancer risk for each type are not fully understood, the results lend further support for the promotion of optimal nutrition, exercise, and weight control as important preventive health measures.

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