Objective <p>To investigate the relationship between ASM/BMI (Appendicular Skeletal Muscle Mass/ body mass index) and low back pain.</p> Methods <p>Participants from the National Health and Nutrition Examination Survey (NHANES 1999 ~ 2004) were included. Multiple logistic regression modeling was used to explore the relationship between ASM/BMI and low back pain.</p> Result <p>A total of 11,738 participants were included in this study, and there were significant differences between the pain group and non-pain group in terms of sex, race, poverty-to-income ratio, and educational attainment. We analyzed ASM/BMI by quartiles into Q1, Q2, Q3, and Q4 into four groups, and the results showed that participants in Q4 had a significantly lower risk of low back pain compared to those in Q1 (<i>p</i> = 0.003); No significant difference in low back pain risk was observed between Q2, Q3, and Q1. Subgroup analyses suggest that the role of elevated ASM/BMI in reducing the risk of low back pain may be more pronounced in women and in individuals aged 40–59 years.</p> Conclusion <p>This study demonstrated that there is a negative correlation between ASM/BMI and low back pain, and that the negative correlation between ASM/BMI and low back pain is more significant in women and in individuals aged 40–59 years. This suggests that incorporating ASM/BMI assessment into clinical evaluations could improve risk stratification for low back pain, particularly in women and middle-aged populations (40–59 years).</p>