Obesity and inactivity could someday account for more cancer deaths than smoking if current trends continue, a leading cancer expert says. As the rate of smoking decreases, other unhealthy habits threaten to offset the progress in reducing cancer deaths, says Richard Wender, a physician and chief cancer control officer at the American Cancer Society (ACS). A study in the New England Journal of Medicine last fall found 13 types of cancer were linked to excess body weight. There's no guarantee that obesity and inactivity will surpass smoking as a cancer cause, Wender says, but the possibility is startling. "Who would’ve thought we’d ever see the day where what you eat (and) exercise, could account for more cancer deaths than smoking?” he asks. The connections between smoking and too much exposure to the sun and cancer are well known, but the connections between nutrition and exercise and cancer are less known and harder to determine. Calculating cancer's link to obesity is difficult in part because of an overlap in cancer risk factors, says ACS' Rebecca Siegel, strategic director of ACS' surveillance information services. Siegel comments that 20% of cancers are caused by poor diet, alcohol consumption, a lack of physical activity and/or excess weight. However, that 20% cannot be combined with the 30% of cancer deaths caused by cigarette smoking since poor people are more likely to be obese and to smoke than those who are more affluent people. A striking 50% of all cancer deaths could be prevented by following the basics of a healthy lifestyle, says Wender. That includes diet and exercise and having regular cancer screenings and getting the HPV vaccine that helps prevent cervical cancer and likely oral cancer and for Hepatitis B, which can lead to liver cancer.