Vol. 284, Issue 2, E416-E423, February 2003
Potassium per kilogram fat-free mass and total body
potassium: predictions from sex, age, and anthropometry
Ingrid
Larsson,
Anna
Karin
Lindroos,
Markku
Peltonen, and
Lars
Sjöström
Department of Body Composition and Metabolism, The
Sahlgrenska Academy at Göteborg University, SE-41345
Goteborg, Sweden
Total body potassium
(TBK) is located mainly intracellularly and constitutes an index of
fat-free mass (FFM). The aim was to examine whether TBK and the
TBK-to-FFM ratio (TBK/FFM) can be estimated from sex, age, weight, and
height. A primary study group (164 males, 205 females) and a validation
group (161 and 206), aged 37-61 yr, were randomly selected from
the general population. TBK was determined by whole body counting, and
FFM was obtained by dual-energy X-ray absorptiometry (DEXA;
FFMDEXA). The primary study group was used to construct
sex-specific equations predicting TBK and TBK/FFM from age, weight, and
height. The equations were used to estimate TBK and TBK/FFM in the
validation group. The estimates were compared with measured values. TBK
in different age ranges was predicted, with errors ranging from 5.0 to
6.8%; errors for TBK/FFM ranged from 2.7 to 4.8%, respectively. By
adding FFMDEXA as a fourth predictor, the error of the TBK
prediction decreased by approximately two percentage units. In
conclusion, TBK and TBK/FFM can be meaningfully estimated from sex,
age, weight, and height.
body composition; dual-energy X-ray absorptiometry; potassium-40; total body potassium-to-fat-free mass ratio; randomly selected study
groups
