Relationship between obesity and foot pain and its association with fat mass, fat distribution, and muscle mass

Objective To examine the relationship between obesity, body composition, and foot pain as assessed by the Manchester Foot Pain and Disability Index (MFPDI). Methods. Subjects 25-62 years of age (n = 136) were recruited as part of a study examining the relationship between obesity and musculoskeletal health. Foot pain was defined as current foot pain and pain in the last month, and an MFPDI score of >= 1. Body composition (tissue mass and fat distribution) was measured using dual x-ray absorptiometry. Results. The body mass index (BMI) in this population was normally distributed around a mean of 32.1 kg/m(2). The prevalence of foot pain was 55.1%. There was a positive association between BMI and foot pain (odds ratio [ OR] 1.11, 95% confidence interval [ 95% CI] 1.06-1.17). Foot pain was also positively associated with fat mass (OR 1.05, 95% CI 1.02-1.09) and fat mass index (FMI; OR 1.16, 95% CI 1.06-1.28) when adjusted for age, sex, and skeletal muscle mass and age, sex, and fat-free mass index (FFMI), respectively. When examining fat distribution, positive associations were observed for android/total body fat ratio (OR 1.42, 95% CI 1.11-1.83) and android/gynoid fat ratio (OR 35.15, 95% CI 2.60-475.47), although gynoid/total body fat ratio was inversely related to foot pain (OR 0.83, 95% CI 0.73-0.93). Skeletal muscle mass and FFMI were not associated with foot pain when adjusted for fat mass or FMI, respectively. Conclusion. Increasing BMI, specifically android fat mass, is strongly associated with foot pain and disability. This may imply both biomechanical and metabolic mechanisms.