Medical research continues to explore the role of diet and nutrition as potential risk factors for various cancer types. Diet-related factors, including obesity, may account for as much as thirty percent in modernized countries. By contrast, these factors are estimated to account for only twenty percent of all new cases. Lifestyle variables in western societies, including diet, use of alcohol, lack of exercise, and excess body mass indices (BMI) all appear to contribute to increased risk for those populations.

Lung cancer is the most prevalent form of the disease worldwide. The association between the disease and smoking has been heavily documented—by some estimates smoking may be responsible for eighty percent of all cases in modernized nations. Historically the disease has been associated with low BMI. A recent study, however, indicates that risk may be increased for obese individuals, both smoking and non-smoking.

Researchers at the University of North Carolina reported that individuals whose BMI was in excess of 30.84 (30 being the benchmark for obesity) were twice as likely to develop the disease. These findings are comparable to other body locations but are actually the opposite of other studies, which identified the disease with lower BMI. Whether these findings are the result of other dietary insufficiencies associated with smoking, or some other factor, remains for future studies to determine. 

The gallbladder stores and secretes bile into the small intestine to help break down fats in the foods we eat. The vast majority of gallbladder cancers are adenocarcinomas, that is, they develop from the cells that line the organ. Among the risk factors are gallstones, smoking, and high carbohydrate/low fiber diet. Most patients with the disease are overweight or obese, and obesity is a major risk factor for the development of gallstones.

Cancerous tumors of the female reproductive system are among the most significant health issues concerning women in the US today.

Cervical cancer is the second most common female carcinoma after breast, with an estimated 500,000 diagnosed annually worldwide. The disease occurs more frequently in younger women. Mortality rates due to cervical cancer are higher among obese women than among their thinner counterparts.

According to a recent study whose results were published in Obstetrics & Gynecology, high adolescent BMI increases the risk of developing pre-menopausal ovarian cancer. While the disease is diagnosed most often after age fifty, no evidence pointed to an increased risk due to adult weight gain.

Medical researchers are uncertain what role obesity might play in these varieties of the disease. So far, being overweight does not appear to have a direct relationship to either of these cancer types.

Excessive body weight may also have an impact on hepatocarcinoma development. New research suggests that the body's internal mechanism in obese individuals may actually cause undigested food to ferment and produce alcohol, which could lead to fatty liver disease. This process is nearly identical to that caused by heavy drinking—the principal cause of this disease. Although fatty liver disease is reversible, if steps are taken to remove the offending agents, an estimated ten percent of all sufferers develop cirrhosis, a pre-cancerous condition.

Thyroid cancer occurs between two and three times more often in women than men; specifically younger women of child-bearing age. Although specific causes, apart from radiation exposure have not been identified, scientists believe that obesity and fat content in the body may also be a risk factor.