In case anyone needs a reminder to stick to that New Year's resolution to slim down or kick the cigarette habit, researchers have confirmed that obesity and smoking are still the country's leading contributors to preventable deaths and illnesses. In fact, the new findings, from a 16-year survey of more than 3.5 million adults, reveal that being overweight has taken the lead as contributing the most to preventable poor health in the U.S.

The results, tabulated from the U.S. Centers for Disease Control's (CDC) Behavioral Risk Factor Surveillance System and published online Tuesday ahead of print in the February issue of American Journal of Preventive Medicine, document what public health officials have long predicted, that with the country's expanding waistlines, widespread health consequences have become increasingly common.

"The total health burden of obesity surpassed the total health impact of smoking," concluded the authors, who are based at the Department of Biostatistics at the Mailman School of Public Health and School of Nursing at Columbia University in New York City and the Department of Community Health and Social Medicine at the Sophie Davis School of Biomedical Education at The City College of New York. They ascribe this shift in large part to the drop in the number of U.S. adults who smoke (from 22.7 percent in 1993 to 18.5 percent in 2008) and the increase in the proportion of people who are obese (from 14.5 percent to 26.7 percent).

When the survey started, in 1993, smoking was by far the leading cause of preventable death and disease. But by the study's conclusion, in 2008, obesity had tipped the scales—increasing in prevalence by 85 percent—to become the primary cause of preventable illnesses and poor health-related quality of life. Smoking, however, still causes more cumulative years to be lost due to premature death. A CDC-sponsored study, published last April in PLoS Medicine, found that as of 2005 smoking was the most frequent killer (causing about one in five deaths), with high blood pressure following up close behind (causing one in six deaths). Obesity came in third at that point, being responsible for almost a quarter of a million deaths—or one in 10.

And although total life expectancy in the U.S. rose by about 3.5 percent between 1993 and 2008, the authors caution that morbidity and mortality from obesity eventually "may result in a decline in future life expectancy." By analyzing the data in terms of health-related quality of life, the researchers found that this metric is already on the decline (it dropped about 2.2 percent during the study period). Obesity alone contributed to a 127 percent drop in a measurement of quality-adjusted life years over the course of the study, the authors report. 

The large dataset was based on telephone surveys of 3,590,540 individuals who reported their recent physical and mental health levels, so no direct medical examination or follow-up took place. (The survey information was matched with the National Death Index to collect mortality figures.) The authors note that, if anything, "these calculations would likely undervalue the total health impact of smoking and obesity." And reporting bias might also have played a role in understating the numbers: "Data shows that participants tend to under-report both smoking and weight and, therefore, the burden of disease due to both smoking and obesity might actually be higher."

Image courtesy of iStockphoto/RBFried