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None of the cutoff points for fat-free mass index (FFMI) were tested for the Brazilian population, and it is unknown whether the available ones are able to discriminate extrapulmonary disease manifestations. This cross-sectional study aims to develop and validate a cutoff point for FFM depletion based on Brazilian patients with chronic obstructive pulmonary disease (COPD) and to verify its association and of previously published cutoffs with extrapulmonary manifestations.A new cutoff point was obtained from the best FFMI value for discrimination of preserved exercise capacity in a sample of patients (n = 57). The discriminative capacity was assessed in another sample (n = 96). The new cutoff point and other previously published ones were tested to discriminate low exercise capacity, physical inactivity, sedentary lifestyle and low quality of life. A receiver operation characteristics curve with area under the curve (AUC) value was plotted and each cutoff points' discriminative capacity was calculated. Cox regression and Kaplan-Meier method assessed the association between the cutoff points and mortality.The new cutoff points for FFMI were 14.65 kg/m2 for women (AUC = 0.744; sensitivity (Se) = 0.88; specificity (Sp) = 0.60) and 20.35 kg/m2 for men (AUC = 0.565; Se = 0.36; Sp = 0.81). The new cutoffs were the best to discriminate poor exercise capacity assessed by walked distance in % predicted and quality of life. Only the new cutoff point was associated with mortality (HR = 2.123; 95% CI: 1.03-4.33, P = 0.039, log rank P = 0.035).Only the new cutoff point was associated with all-cause mortality, and it had the highest discriminating capacity for exercise capacity and quality of life in Brazilian patients with COPD.