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 between 1998 and 2009.
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 (average height, 6 feet) were 44 percent more likely to have low back pain, compared with the shortest males (average height, 5 feet 5 inches). Tall females (average height, 5 feet 7 inches) were 22 percent more likely to have back pain than the shortest females (average height, 5 feet 1 inch).
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 who was not involved in the research. "This paper should stimulate other researchers to look at young people to see if there is a way to minimize their symptoms."
Joints that carry more weight or that are longer may be at more risk for developing pain, said Heidi Prather, an associate professor physical medicine and rehabilitation at Washington University, St. Louis who was not involved in the study.
She said low back pain is the No. 1 cause of disability in people under the age of 45.
"So many of us get low back pain," she said. "There is no magic bullet."
Some measures that may help are maintaining a healthy weight, doing flexibility exercises, core muscle training exercises and regular aerobic exercises, especially those that involve high intensity and low impact, such as brisk walking, rowing, swimming and using an elliptical training machine, she said.
"Sleep is really important in preventing low back pain," she added.
The best mattress is the one that is firm enough for support but soft enough to allow for a good night's sleep, she said.