Increased Body Mass Linked to Back Pain

Increased back pain among individuals who are overweight or obese is specifically related to increased body fat content, according to data from a study published in the September 15 issue of Spine.

With further research, interventions to prevent increased fat mass may help to reduce the risks of back pain and related disability, concluded lead author Donna M. Urquhart, PhD, of Monash University, Melbourne, Australia.

The study included 135 participants, ranging from normal weight to obese, all of whom completed a standard questionnaire to measure low back pain intensity and related disability. Participants also underwent a dual-energy x-ray absorptiometry for detailed assessment of body composition, including measurement of fat and lean body mass. The results showed that heavier individuals experienced higher levels of back pain intensity. For each 5-unit increase in body mass index (BMI)—equivalent to the difference between being classified as overweight or obese—the odds of high-intensity back pain increased by 35%. For back pain disability, the association was even stronger: 66% per five-unit increase in BMI.

However, the increase in back pain at higher BMIs was specifically related to increased fat mass. For each 5-kg increase in body fat mass, the odds of high-intensity back pain increased by 19%. For increased fat mass in the lower limbs, the increase was 51%.

In contrast, lean body mass was unrelated to back pain. Therefore, the increase in back pain intensity among individuals with higher BMIs was wholly related to their higher body fat content—not just the fact that they were heavier. Individuals with higher body fat also had increased disability from back pain.

Back pain and disability were also related to specific patterns of body fat—including increased fat in the trunk area, android fat mass, and gynoid fat mass. On adjustment for possible confounding factors, no measures of lean tissue mass were associated with higher pain intensity or disability, the authors wrote.

The new study is the first to look at how back pain is related to more detailed measures of body fat—including specific patterns of fat and lean mass distribution.

The results show that greater fat mass is specifically associated with increased back pain and disability, while lean tissue mass is not. Several factors likely contribute to the link between fat mass and back pain, including greater mechanical demands on the spine. Metabolic factors related to higher fat mass—such as increased inflammatory activity—may also play a role.

Because of its cross-sectional design, the study can’t determine which comes first: increased fat mass or back pain. Longitudinal studies are needed to determine whether higher fat mass predicts the later development of low back pain. If that is the case, measures to control body fat might be effective in preventing back pain and related and disability.