CHICAGO — A study of more than 800,000 young adults found that obesity and height increased the risk of having low back pain.

“The most simple explanation for that correlation is that the mechanical load of overweight and body height (on the lever arm) may cause early failure of the back-supporting mechanism and cause early (low back pain) complaints,” said lead author Oded Hershkovich, an orthopedic surgeon in Israel.

The study, which was presented Friday at a national meeting of spine surgeons, involved 17-year-old male and female Israeli military recruits who had undergone medical exams before service induction.

The risk of low back pain was relatively low in both male and female recruits. Obese males were 16 percent more likely to have low back pain; for females it was 21 percent.

Height also increased risk. The tallest males were 44 percent more likely to have low back pain, compared with the shortest males. Tall females were 22 percent more likely to have back pain than the shortest females.

The study did not look at what might have caused the low back pain, only the correlations between back problems and weight and height. But it measured subjective complaints from the military recruits as well as objective findings from spine exams.

“You can do something about your weight, but not your height,” said Thomas Dreisinger, a San Diego exercise physiologist.