Evaluation of body fat estimated from body mass index and impedance in Belgian male military candidates: comparing two methods for estimating body composition.
OBJECTIVE
The study objective was to evaluate whether a classification based on body mass index (BMI) agrees with a classification based on body fat mass, estimated by bioelectrical impedance.


METHODS
A random sample of 448 male candidates between 18 and 20 years was selected during their medical visit in a military recruitment center. BMI was determined as weight/height2 and was considered normal between 20.0 and 25.0 kg/m2 (cfr. WHO classification). Percentage of body fat was estimated with bioelectrical impedance, using the Omron Body Fat Analyzer HBF-306. Subjects with a body fat percentage measured by bipolar bioelectrical impedance analysis (BF%(IMP)) < or = 20.9% were considered normal weight, while subjects with a BF%(IMP) > or = 21.0% were considered overweight. We used the following classification: true positives were normal scores for BMI and impedance; false positives were normal scores for BMI but not for impedance; true negatives were overweight scores for BMI and for impedance; and false negatives were overweight scores for BMI but not for impedance. Data were analyzed using the SPSS statistical program.


RESULTS
BMI ranged from 17.0 to 29.4 kg/m2; percentage of fat mass varied between 5.3 and 31.4% of body weight. Of the total sample, 328 (73.2%) candidates were classified as true positive, 29 (6.5%) as false negative, 47 (10.5%) as false positive, and finally 44 (9.8%) as true negative. The difference in classification in normal weight versus overweight between the BMI method and the bipolar bioelectrical impedance method was statistically significant (chi2 with one df = 86.04; p < 0.001).


CONCLUSIONS
To limit false-negative classifications, additional impedance measurements in the BMI category between 25.0 and 27.0 kg/m2 is mandatory to determine whether there is really an excess fat mass.
Mullie
Patrick
P
Unit of Epidemiology and Biostatistics, Queen Astrid Military Hospital, Bruynstraat 1, B-1120 Brussels, Belgium.
Vansant
Greet
G
Hulens
Mieke
M
Clarys
Peter
P
Degrave
Etienne
E
D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D000886:Anthropometry; D001530:Belgium; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D006304:Health Status; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008887:Military Medicine; D008889:Military Personnel; D009765:Obesity; D050177:Overweight