Background Childhood overweight and obesity are increasingly significant problems, strongly related with adulthood obesity and associated morbidity. Body mass index (BMI) is the first screening tool for all children coming in for a well child visit. BMI should be calculated and plotted on a growth chart. BMI levels correlate with body fat and with concurrent health risks.

Methods and materials The study included 2770 adolescents: 1397 boys (50,4%) and 1373 girls (49,6%). Our aim was to evaluate anthropometric data (weight, height, BMI through the percentilic method, to assess the percentage of adipose tissue by bioelectric impedance, waist circumference and thigh circumference).

Results The medium age of children included in the study was 12,55±1,7 years. Data analysis put in evidence overweight in 14,3% cases (395 children: 222 boys and 73 girls) with a BMI between 85 and 94 percentile. Obesity was found in 2,7% cases with a BMI > the 95^th percentile (74 children: 47 boys and 27 girls). Adipose tissue excess was confirmed in 454 adolescents (16,4%) – 333 boys (23,8%) and 121 girls (8,8%). The value of waist circumference higher than 90 percentile was evaluated in 99 adolescents (3,6%) – 21 boys (1,5%) and 78 girls (5,7%).

Conclusion BMI is a simple, inexpensive and noninvasive surrogate measure of body fat, because it is a measure of excess weight rather than excess body fat. The clinical limitations of BMI should be considered. Nevertheless, BMI should be calculated and documented in the medical record on all children ages 2–18 at least annually, ideally at a well child visit.