Limb fat-free mass and fat mass reference values by dual-energy X-ray absorptiometry (DEXA) in a 20-80 year-olditalian population

To establish reference values for limb composition, fat-free mass (FFM) and fat mass (FM) in Italian adults for gender-specific age brackets 20-80 years old and to assess age-related regional changes in body composition. A multicenter, retrospective study was conducted on 1571 healthy subjects, 1240 women and 331 men. Regional FFM and FM were measured by dual-energy X-ray absorptiometry. FM was expressed as % of limb weight. FFM in men diminished with age in both arms and legs, with reference ranges (25th -75th percentile) of 3.8-4.6 kg and 10.4-12.2 kg, respectively for 20-29 year-olds, and 3.1-3.9 kg and 8.2-10.4 kg for 70-79 year-olds. Women's arm FFM remained stable with aging (reference values 1.7-2.2 kg), decreasing in their legs (6.2-7.2 kg for 20-29 year-olds, 5.5-6.5 kg for 70-79 year-olds). Limb FM% increased with age in both genders: the reference values were 9-15% (arms) and 12-21% (legs) for 20-29 year-old men, and 19-26% and 19-29%, respectively, for 70-79 year-olds; for women's arms, they were 25-36% for 20-29 year-olds and 36-48% for 70-79 year-olds, while their leg FM remained the same with aging, i.e. 32-40%. These data complete the published reference values for whole body composition, enabling physiological or pathological changes in limb composition to be identified in Caucasian populations living in the Mediterranean area