Metabolism matters
By Richard Saltus
Matt Vander Heiden is one of several researchers probing how and why body weight, exercise, and diabetes influence cancer risk.
Last October, a widely cited report warned that being even somewhat overweight increases the risk of six common types of cancer, including colon, kidney, and breast cancer in postmenopausal women.
"Science is telling us today that even small amounts of excess body fat, especially if carried at the waist, increase one's risk," said a spokesman for the International Obesity Taskforce. Being overweight also increases the risk of esophageal, uterine, and pancreatic cancers, said the report, released by the American Institute for Cancer Research and the World Cancer Research Fund and based on an analysis of 7,000 studies.
This mounting connection between body weight and cancer, validated in study after study, is prompting deep concern at a time when approximately two-thirds of the U.S. population is classified as overweight or obese. American Cancer Society researchers estimate that about 14 percent of cancer deaths in men, and 20 percent in women, in this country are due to excess weight and obesity. Moreover, the obesity epidemic has caused an alarming surge in Type II diabetes – which also makes people more cancer-prone.
"It's becoming increasingly clear that metabolic factors … predispose people to a wide range of cancers."
"It's becoming increasingly clear that metabolic factors such as obesity, lack of exercise, and diabetes predispose people to a wide range of cancers," says Bruce Spiegelman, PhD, a Dana-Farber cancer biologist who has discovered important molecular regulators in obesity and diabetes. "But it's not so clear how these conditions actually alter an individual's risk of cancer, and that's what we're trying to find out."
Imbalances in metabolism – the processing of food into fuel and the resulting energy expenditure to operate the body – play a role in many serious public health problems, from heart disease to cancer. But how, exactly, do extra pounds, high blood sugar, or a couch-potato lifestyle translate into elevated odds of cancer? The question is complicated but attracts increasing levels of research interest. In recent years, the National Cancer Institute has been funding an initiative aimed at reducing cancer incidence and mortality associated with obesity, low physical activity, and poor diet.
Teasing out the chains of molecular events linking metabolism and cancer would likely allow more-precise lifestyle recommendations, and also could lead to new "chemoprevention" drugs. "This is becoming a big area of research," says Charles Fuchs, MD, MPH, who directs the Gastrointestinal Malignancies Program of the Dana-Farber/Harvard Cancer Center. "It could have a dramatic influence on therapies in the next five years."
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