If you've broken your New Year's resolution to eat better and exercise more, here's a reason to hop back on the healthy-living bandwagon. A new study from the Centers for Disease Control and Prevention (CDC) finds that diet and inactivity may soon overtake smoking as the leading cause of death in the United States. Some 2.4 million people died in the US in the year 2000, most of them from heart disease, cancer, and stroke. The CDC researchers analyzed what factors led to the deadly diseases in the first place. Although most diseases have multiple causes, the scientists were able to estimate how much things like smoking, diet, infections, or drinking contributed to the deaths. Their findings were published in the Journal of the American Medical Association (Vol. 291, No. 10: 1238-1245). Tobacco use was responsible for about 435,000 of the deaths in 2000, while bad diet and physical inactivity accounted for about 400,000. That ratio is likely to change, though, because the number of Americans who smoke is slowly dropping, while the number of overweight and obese Americans is growing rapidly. 8th street latinas "The impact of diet and inactivity is substantial, has increased, and is a very important challenge to the health of Americans," said Michael McGinnis, MD, MPP, who published a similar analysis in 1993 and wrote an editorial accompanying the current report. His study, based on data from 1990, also found that smoking and diet/inactivity were the leading killers in the US. Trends of smoking and overweight among youth are of particular concern because of the impact these trends will have on future rates of cancer, heart disease, and diabetes, said Colleen Doyle, MS, RD, Director of Nutrition and Physical Activity for the American Cancer Society. The CDC researchers estimate that one-third of all US deaths are due to diseases related to diet, physical inactivity, and smoking. However, the specific links to cancer may be even stronger. Mike in Brazil It is estimated that about one-third of all cancer deaths in the US are related to smoking, while about another third are linked to diet, excess weight, and physical inactivity. For the majority of Americans who do not smoke, dietary choices and physical activity are the most important factors we can control in terms of cancer risk. Public Policy, Personal Responsibility The numbers point to a critical need for action, both from individuals and society as a whole, said McGinnis, of the Robert Wood Johnson Foundation. "Behavior is only the end product of a long line of influences and we need to make sure we address our attention to all elements along the spectrum," he said.