The Relationship Between Low Back Pain, Obesity and Physical Activity
Obesity and LBP combined make up for about 30 per cent of U.S. health care costs. More evidence is supporting an association between obesity and low back pain (LBP) but, not much is known about the relationship between the two. Obesity is listed as a impacting factor in LBP mostly described through the body mass index (BMI). Body mass index is categorized as: normal weight <25, overweight 25-30, obese 31-35, and ultraobese 36+. Physical activity is a logical suspect to connect obestiy and lower back pain, but no study has demonstrated the role of physical activity. Exercise and weight loss is know to benefit some with back pain, yet the role that physical activity plays is unclear. This study looked into the relationships between LBP, obesity and physical activity.

To collect data on the relationships between obesity, LBP and physical activity information was obtained through participant surveys, physical examinations, and for 7 days the participants wore accelerometers. (Accelerometers can measure in real-time, duration and intensity of motion). Participants wore the accelerometer while they were awake and every minute of that time was used to calculate activity level.

Once the data was collected the findings were very interesting. First, the baseline risk of LBP increased with increased BMI. Smoking was consistently a strong predictor of LBP across any BMI level. WIth overweight subjects it was found that time spent doing sustained activity in a moderate range reduced the odds of having LBP and was even protective from getting LBP. For the average overweight American increasing time doing moderate activity by 17.6 minutes a day, decreases the risk of getting LBP by 32 per cent! In obese subjects, time spent in sedentary activity states had positive relationship with increased LBP. In the morbidly obese category more time spent in moderate activity reduced odds of getting LBP. A small increase in moderate activity level for the morbidly obese by 2.1 minutes reduces back pain risk by 38 per cent!

This study shows that there is a relationship for increased BMI being a risk factor for LBP. Reduced physical activity is also a risk factor for getting LBP, lots of sedentary time and reduced moderate activity have a greater impact on increased LBP risk in overweight Americans. In the overweight population physical activity can be a dimishing factor in lower back risk and it does not take great increases in physical activity to for exercise to have a protective effects.
References
Smuck, M; Kao, MCJ; Brar, N.; Martinez-Ith, A.; Choi, J; Tomkins-Lane, CC. Does physical activity influence the relationship between low back pain and obesity?. The Spine Journal. February 2014. Vol. 14. No. 2. Pp. 209-261.