Does body composition differ between fibromyalgia patients and controls? the al-Ándalus project.

OBJECTIVES: To characterise the anthropometric and body composition profile of a sample of fibromyalgia women and men from southern Spain and compare them with non-fibromyalgia controls.
METHODS: The cross-sectional study comprised 566 (51.9 ± 8.3 years) fibromyalgia women vs. 249 (49.3 ± 9.9 years) control women; and 24 (47.0 ± 8.4 years) fibromyalgia men vs. 56 (49.7 ± 11.5 years) control men. Body composition and cardiorespiratory fitness were assessed by means of a bioelectric impedanciometer and the 6-minute walk test, respectively.
RESULTS: All body composition para-meters (except muscle mass) differed between fibromyalgia and control women (all, p<0.01) even after controlling for several key variables (all, p<0.05). The effect sizes observed were small-medium. When cardiorespiratory fitness was included as covariate, body composition was no longer different between the women study groups. No differences in body composition were observed between fibromyalgia and control men (all, p>0.05). Weight status differed between women groups, with 11% lower normal-weight and 17% higher obesity prevalence for the fibromyalgia women group (p<0.001), but not between men groups (p=0.711). Seventy-two percent of the fibromyalgia women and 79% of the fibromyalgia men were overweight-obese. Sixty-one percent of the control women and 83% of the control men were overweight-obese.
CONCLUSIONS: Obesity is a greater common condition among fibromyalgia women compared to their counterparts from southern Spain, which might be explained by lower levels of cardiorespiratory fitness in fibromyalgia. However, fibromyalgia and control men do not differ on either body composition or weight status, in spite of the lower cardiorespiratory fitness found in the fibromyalgia men group.