Foot pain is associated with obesity, however change in foot pain following weight loss has been largely unexplored. Furthermore, the association between obesity and foot pain may be more strongly linked with body composition, as opposed to body mass. This project aims to investigate i) if surgical weight-loss reduces foot pain, ii) if baseline body composition or body mass predicts change in foot pain.
Participants were recruited from the surgical waiting lists at two tertiary hospitals in Adelaide, South Australia, for this repeated-measures cohort study. A treatment group was recruited for baseline measures immediately before bariatric surgery and re-evaluated again six-months postoperatively. The control group was recruited from the same waiting lists, but these patients were not scheduled to have surgery within six-months. Participants in the control group were re-evaluated at six-months follow-up. Foot pain was assessed with the Manchester-Oxford Foot and Ankle Questionnaire. Weight and height were measured, and body mass index (BMI) was calculated. Body composition was analysed with dual-energy X-ray absorptiometry, from which fat mass index (FMI) and fat-free mass index (FFMI) were calculated. Multivariable linear regression models were used to determine predictors of change in foot pain between baseline and follow-up.
Forty-five participants, 38 women and seven men, with a mean (SD) age of 45.7 (9.4) years were recruited for this study. Twenty-nine participants (BMI = 44.8 (7.0) kg) underwent bariatric surgery, while 16 (BMI = 47.9 (5.2) kg) remained on the waiting-list. Using multivariable analysis, surgical weight-loss was significantly associated with reduced pain at follow-up (b-32.6, 95% CI -43.8 to -21.4) A secondary analysis revealed that FMI (b1.5, 95% CI 0.2 to 2.8), but not FFMI (b-1.4, 95% CI -3.4 to 0.5), was independently associated with increased pain at follow-up, controlling for age, gender and depressive symptoms.
Discussion and Clinical Relevance
Surgical weight-loss is clearly associated with a significant reduction in foot pain. Higher baseline FMI, but not FFMI, was predictive of increased foot pain at follow-up, suggesting a non-mechanical relationship between obesity and pain. Further study may focus on non-surgical weight-loss with larger samples and specific foot pathologies.