Body Mass Index (BMI). According to WHO there are four classes of BMI: weight deficit (<18.5 kg / m2) normal weight (18.5 to 24.9 kg / m2) overweight (25.0 to 29.9 kg / m2) obesity (> 30 kg / m2), the latter being subdivided into three classes: - grade I obesity (30.0 to 34.9 kg / m2) - grade II obesity (35.0 to 39.9 kg / m2) - grade III obesity (≥40 kg / m2)