Considering the negative effects of low physical activity, this study presents the values (and increases) of individual somatic features and body proportion indicators considered to be deter- minants of being overweight and obese among the examined girls and boys in view of differenti- ated physical activity. The research material includes the results of a two-year study of girls and boys aged 7–9. It involved 253 pupils: 167 from general classes and 86 from sports classes (sports acrobatics classes). Three series of measurements were carried out, covering a 2-year period of early primary education. As part of the research, measurements of body height and mass, waist circumference, hip circumference and the thickness of skin and fat folds were measured. The body proportions were calculated based on anthropometric measurements. In the analyzed period of ontogenesis (ages 7–9), pupils from general classes, when compared to those from sports classes, were distinguished by higher parameters of obesity indicators, increasing the risk of developing metabolic diseases. Children from the general classes, in contrast to those from the sports ones, were characterized by a higher Body Mass Index, waist and hip circumference, thickness of skin and fat folds, and waist-to-height ratio.