Fat-free mass index: changes and race/ethnic differences in adulthood

Abstract

Objective Nutritional status is assessed by measuring BMI or percent body fat (%fat). BMI can misclassify persons who carry more weight as fat-free mass and %fat can be misleading in cases of malnutrition or in disease states characterized by wasting of lean tissue. The fat-free mass index (FFMI) is proposed to assess body composition in individuals who have a similar body composition but differ in height allowing identification of those suffering from malnutrition, wasting or those that possess a relatively high muscle mass. The purpose was to determine whether the FFMI differs in a group of racially/ethnically diverse adults. Design Cross-sectional. Subjects Subjects were a multi-ethnic sample (Caucasian, CA; African American, AA; Hispanic, HIS and Asian, AS) of 1339 healthy males (n = 480) and females (n = 859) ranging in age from 18–110 years. Total body fat, total fat-free mass and bone mineral density were estimated using dual energy X-ray absorptiometry. Results FFMI differed among the four ethnic groups (P ≤ 0.05) for both genders. A curvilinear relationship was found between age and FFMI for both genders although the coefficients in the quadratic model differed between genders (P ≤ 0.001) indicating the rate of change in FFMI differed between genders. The estimated turning point where FFMI started to decline was in the mid 20s for male and mid 40s for female participants. An age × gender interaction was found such that the rate of decline was greater in male than female participants (P ≤ 0.001). For both genders, FFMI was greatest in AA and the least in AS (P ≤ 0.001). There was no significant interaction between race and age or age2 (P = 0.06). However, male participants consistently had a greater FFMI than female participants (P ≤ 0.001). Conclusions These findings have clinical implications for identifying individuals who may not be recognized as being malnourished based on their BMI or %fat but whose fat-free mass corrected for height is relatively low.

Total and regional relationship between lean and fat mass with increasing adiposity—impact for the diagnosis of sarcopenic obesity

“…37,38 In addition, the relationship between fat and lean mass is known to be influenced by ethnicity. 18 As we only investigated Caucasians, our results are not transferable to other ethnic groups.…”

“…17 In women, FFMI was consistently lower with increasing age group after the age of 20 years, whereas in men this occurred after the age of 40 years (Figures 1a and b). By contrast, Hull et al 18 showed FFMI to peak with age 45 years in women and 25 years in men with a subsequent decrease thereafter. Barlett et al 19 demonstrated the ratio of FFM/height to remain stable till age 50 years in women with a decrease afterwards and a nonsignificant decline in men 460 years.…”

Body composition phenotypes in pathways to obesity and the metabolic syndrome

“…The study by Hull et al 9 also reported a curvilinear relationship between age and FFMI for both genders, and that there was a gender difference in the rate of change in FFMI with age. Declines in FFMI were found at an earlier age in male subjects, whereas decline in female subjects occurred in the late 40s.…”

“…8 As pointed out by Hull et al, 9 in hospitalized individuals, recognition of malnutrition inferred from BMI is particularly important because nutritional status is related to longevity and mortality, influences the course of a disease and optimal treatment and affects the length of hospital stay. By comparing values of an individual patient with national norms, the health professional is able to assign a level of fatness, determine the level of risk for chronic disease and estimate mortality risk.…”

“…For both genders, total body potassium values were highest in African Americans and the least in Asians. 28 In a recent study, using DEXA for assessing body composition, Hull et al, 9 investigating whether FFMI differs in 1339 healthy adults (age 18-110 years) of different races and ethnicity (Caucasian vs African American, Hispanic and Asian), found that FFMI differed among the four ethnic groups for both genders (males4 females), with FFMI greatest in African Americans and the least in Asians. These highlight racial disparities in body composition and suggest that identification of individuals by race will show greater susceptibility for disease related to loss of FFM.…”