[Adipose tissue contents and body mass index in adults]

The aim of the study was to verify, in epidemiological setting, the hypothesis that at a given body mass index the contents of adipose tissue (AT%) varies with age and is larger in older people.

To verify this assumption population-based data were used. Measurements were obtained in 3359 men and women, aged 30-72 and living in two large towns of Upper Silesian Industrial Zone (Poland). During home visits each subject was weighted, their posture was measured and AT% was obtained using bioelectrical impedance method. According to body mass index (BMI in kg/m2) the subjects were divided into eight groups (I - BMI: 20.0-22.5; II - BMI: 22.6-25.0 ... VII - BMI: 35.0-37.5; VIII - BMI: 37.6-40.0). Within each BMI group four classes of ages were identified: 30-39 years; 40-49 years; 50-59 years; 60-72 years.

Mean values of AT% increased with age in each BMI group, both in men and women, and the within-BMI group differences were statistically significant (ANOVA). The effect was consistent, however it was more apparent at low BMI values. For consecutive BMI groups (I-VII) the AT% mean values in extreme age groups (30-39 years and 60-72 years) were as follows: I: 21.3+/-5.9% and 28.1+/-7.1%; Il: 22.5+/-6.4% and 29.7+/-6.7%; III: 25.8+/-6.2% and 32.6+/-6.2%; IV: 28.1+/-6.5% and 35.1+/-5.9%; V: 32.3+/-5.8% and 38.4+/-5.6%; VI: 37.2+/-6.5% and 40.9+/-5.5%; VII: 39.2+/-3.9% and 43.5+/-5.7%; VIII: 40.0+/-7.2% and 46.3+/-3.4%, respectively. In subjects with BMI < 25.1 kg/m2 the difference in AT% between the youngest and the oldest group reached seven points, with a relative difference of 30%.

The findings confirmed that BMI value is not a perfect surrogate in the assessment of adipose tissue contents and this fact should be taken into account in epidemiological investigations into risk factors of obesity and its health consequences.