BMI, skinfold thickness, and circumferential measures were assessed in groups of normal healthy Czech boys (n = 1764) and girls (n = 1762) 3-6 years of age in the late 1950s and 1960s (sample C), in the 1990s (sample B), and in 2014-2016 (sample A). During these decades BMI has not changed significantly, and in selected groups (boys 3, 5, and 6, girls 3 and 6 years) it was most recently found to be significantly lower (P ≤ 0.05). Subscapular, suprailiac, triceps, midthigh, and above patella skinfold thicknesses significantly increased in sample A as compared to sample C (P ≤ 0.001). Comparison of the same skinfolds measured in the nineties (sample B) and more recently (sample A) showed similar increase of subcutaneous fat (P ≤ 0.001). The increase of adiposity characterized by skinfolds occurring in spite of not markedly changed BMI indicates significant changes of body composition-latent (also hidden) obesity. The increase of adiposity was relatively greatest on the trunk (P ≤ 0.001)-which is considered a marker of the greatest health risk. The decrease of femoral circumference (P ≤ 0.05) along with simultaneous increase of thigh skinfold (P ≤ 0.01) revealed the decrease of muscle mass in the lower extremity, obviously due to the reduction of weight-transferring physical activity.