Comparison of skeletal muscle mass to fat-free mass ratios among different ethnic groups.
BACKGROUND
Asians seem to have less skeletal muscle mass (SMM) than other ethnic groups, but it is not clear whether relative SMM, i.e., SMM / height square or SMM to fat-free mass (FFM) ratio, differs among different ethnic groups at the same level of body mass index (BMI).


OBJECTIVE
To compare the SMM to fat-free mass (FFM) ratio as well as anthropometric variables and body composition among 3 ethnic groups.


METHODS
Three hundred thirty-nine Japanese, 343 Brazilian, and 183 German men and women were recruited for this cross-sectional study.


METHODS
Muscle thickness (MTH) and subcutaneous fat thickness (FTH) were measured by ultrasound at nine sites on the anterior and posterior aspects of the body. FTH was used to estimate the body density, from which fat mass and fat-free mass (FFM) was calculated by using Brozek equation. Total SMM was estimated from ultrasound-derived prediction equations.


RESULTS
Percentage body fat was similar among the ethnic groups in men, while Brazilians were higher than Japanese in women. In German men and women, absolute SMM and FFM were higher than in their Japanese and Brazilians counterparts. SMM index and SMM:FFM ratios were similar among the ethnic groups in women, excluding SMM:FFM ratio in Brazilian. In men, however, these relative values (SMM index and SMM:FFM ratio) were still higher in Germans. After adjusting for age and BMI, the SMM index and SMM:FFM ratios were lower in Brazilian men and women compared with the other two ethnic groups, while the SMM index and SMM:FFM ratios were similar in Japanese and German men and women, excluding SMM:FFM ratio in women.


CONCLUSIONS
Our results suggest that relative SMM is not lower in Asian populations compared with European populations after adjusted by age and BMI.
Department of Health and Exercise Science, University of Oklahoma, Norman, OK 73019, USA.
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Abe
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Bemben
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Kondo
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Kawakami
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Fukunaga
D050154:Adiposity / Q000208:ethnology*; D000328:Adult; D000367:Age Factors; D000465:Algorithms; D001823:Body Composition; D015992:Body Mass Index; D001938:Brazil; D003430:Cross-Sectional Studies; D005260:Female; D005858:Germany; D006801:Humans; D007564:Japan; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D009929:Organ Size; D050177:Overweight / Q000453:epidemiology / Q000208:ethnology; D012727:Sex Characteristics; D050151:Subcutaneous Fat / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014463:Ultrasonography; D055815:Young Adult