BACKGROUND: The prevalence of obesity in developed countries has reached alarming levels, doubling in the United States since 1980. Although obese patients with chronic low back pain are frequently advised to lose weight, the association between these medical conditions remains unproven. PURPOSE: This study prospectively assessed clinically reported changes in chronic axial low back pain symptoms after weight reduction from bariatric surgery for morbid obesity. STUDY DESIGN: Prospective longitudinal study. PATIENT SAMPLE: Fifty-eight consecutive patients with morbid obesity and chronic axial low back pain undergoing bariatric surgery over a period of 6 months. Patients were considered morbidly obese if they were 50% to 100% above their ideal body weight or having a body mass index (BMI) greater than 40. OUTCOME MEASURES: Visual Analog Scale (VAS) for axial low back pain, Short Form-36 (SF-36) Health Survey, and Oswestry Disability Index (ODI) METHODS: Patients undergoing weight reduction surgery were assessed preoperatively and postoperatively at 12 months with validated clinical measures for axial back pain and disability (VAS, SF-36, and ODI). Bariatric surgery parameters included demographic data, weight, and BMI. Statistical analysis included paired t tests and multiple regression techniques. RESULTS: Of the initial 58 patients, 38 (65%) completed both preoperative (Pre-Op) and postoperative (Post-Op) questionnaires at 12 months. These 38 subjects included 30 women and 8 men, with an age range of 20 to 68 years (mean 48.4+/-10.1). Overall, these patients showed a decrease in mean weight from 144.52+/-41.21kg Pre-Op to 105.59+/-29.24 Post-Op (p<.0001) and BMI from 52.25+/-12.61kg/m(2) Pre-Op to 38.32+/-9.66 Post-Op (p<.0001). Patients demonstrated a statistically significant mean 44% decrease in axial back pain on the VAS scale (p=.006; 5.2+/-3.35 Pre-Op, to 2.9+/-3.1 Post-Op). Analysis of the SF-36 major components revealed that patients experienced significant increases in mean physical health by 58% (p<.0001; 44.5+/-20.09 to 70.24+/-26.84) and in median mental health by 6% (p=.03; 70+/-7.14 to 73.39+/-11.78). Patients also showed statistically significant 24% decrease in Post-Op ODI score for physical disability (p=.05) from 26.75+/-16.56 Pre-Op to 20.35+/-18.71 Post-Op (p=.05). CONCLUSION: This study suggests that the substantial weight reduction after bariatric surgery may be associated with moderate reductions in preexisting back pain at early-follow-up. This effect did not appear to be the result only of an overall improvement in well-being associated with weight loss. However, larger randomized controlled clinical studies with longer-term follow-up are needed to definitively determine a causal relationship.