Researchers say that, unfortunately, the other 97.3 percent of American adults get a failing grade on healthy lifestyle habits.
The study looked at data on more than 4,700 people who took part in the U.S. National Health and Nutrition Survey. The researchers assessed how many people followed four general "principles of healthy living" -- a good diet, moderate exercise, not smoking and keeping body fat under control.
"The behavior standards we were measuring for were pretty reasonable, not super high. We weren't looking for marathon runners," said study senior author Ellen Smit, an associate professor at the OSU College of Public Health and Human Sciences, in Corvallis.
In fact, the standards used in the study are typical of lifestyle advice given by doctors to their patients, Smit's team said. People who adhere to those four behaviors can help reduce their risk of many health problems, including type 2 diabetes, heart disease and cancer.
Unfortunately, less than 3 percent of the adults in the study achieved all four of the healthy living measures, the researchers found.
Overall, 71 percent of the adults surveyed did not smoke, 38 percent ate a healthy diet, 10 percent had a normal body fat percentage and 46 percent got sufficient amounts of physical activity.
Sixteen percent had three of the healthy lifestyle behaviors, 37 percent had two, 34 percent had one and 11 percent had none.
Among the other findings: women were more likely than men to not smoke and to eat a healthy diet, but they were less likely to have adequate physical activity levels. And when it came to race, Mexican-Americans were more likely to eat a healthy diet than blacks or whites.
The study was conducted by researchers at Oregon State University, the University of Mississippi and the University of Tennessee-Chattanooga.
In terms of public health, the findings are disappointing, Smit said in an OSU news release.
"This is pretty low, to have so few people maintaining what we would consider a healthy lifestyle," she said. "This is sort of mind boggling. There's clearly a lot of room for improvement."
Further research is needed to identify ways to get American adults to adopt more healthy lifestyle habits, the experts said.
The study was published recently in the journal Mayo Clinic Proceedings.