Americans are dying younger and living their later years with more diseases than citizens of poorer countries that spend far less than the U.S. on health care, according to a new study.

The most surprising finding, the researchers said, was that the No. 1 risk factor contributing to the burden of disease is the simplest of things: diet.

“That was very powerful for us—something we did not expect,”Ali Mokdad told the CrossFit Journal. He was one of 500 scientists from around the world who worked on the study titled The State of US Health, 1990-2010: Burden of Diseases, Injuries, and Risk Factors. The Journal of the American Medical Association published the study today

Scientists were expecting tobacco and high blood pressure to continue to be the usual suspects, Mokdad said. Instead, tobacco ranked second, followed by obesity, high blood pressure, high fasting plasma glucose level and physical inactivity or low activity.

“What we eat, what we put in our mouth is the major cause of morbidity and mortality,” Mokdad said. “It makes sense. For us to be able to document it and to go back in (the) past and show how this has been changing over the past two decades is very powerful.”