The association between obesity, as defined by a body mass index of 30 or higher, and risk of a variety of types of cancer has received a considerable amount of attention in recent years. Obesity has been associated with an increased risk of esophageal cancer, pancreatic cancer, colorectal cancer, breast cancer (among postmenopausal women), endometrial cancer, kidney cancer, thyroid cancer, and gallbladder cancer. Obesity may also lead to increased cancer-related mortality.
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Mechanisms
The mechanisms by which obesity may increase the risk of cancer are not well understood, but it is believed that the combined effects of the adipose tissue environment and the endocrine alterations that accompany it among obese people both interact to promote tumor initiation and progression. Adipose tissue also creates an inflammatory environment that enhances the ability of tumor cells to metastatize.
Bladder cancer
Obesity is associated with an increased risk of bladder cancer.
Breast cancer
Obesity has been found to decrease the risk of breast cancer among African and Caucasian women, but increase it among Asian women. Obesity is also associated with decreased survival among women with breast cancer, regardless of whether the cancer is pre- or post-menopausal.
Colorectal cancer
Both general and central obesity are associated with an increased risk of colorectal cancer (CRC). The relative risk among obese people relative to those of normal weight has been reported to be 1.334. An association between increased BMI and risk of colorectal adenoma has been reported, as has a dose-response relationship between BMI and colorectal adenoma risk. Increased BMI also increases all-cause mortality and mortality from CRC specifically among people diagnosed with CRC.
Lung cancer
Obesity has been found to protect against lung cancer, especially among those who smoke or have smoked cigarettes.
Renal cell cancer
Obesity is a risk factor for renal cell cancer.
Thyroid cancer
Obese people are at a higher risk of thyroid cancer than are their normal weight counterparts.