PURPOSE: To determine the influence of under- or overweight and obesity on force and power production as well as on lower limb asymmetry. METHODS: A cross-sectional study including 14- to 15-year-old adolescents was performed. Anthropometric measures and 20-m sprint time were measured and countermovement jump (CMJ) was measured. Force and power production were determined using a portable force plate. RESULTS: CMJ and 20-m sprint performances were significantly influenced by BMI categories (both, p<0.001), with obese subjects performing worse than their normal weight counterparts. Peak force and peak power were significantly higher (p < 0.001), especially in obese adolescents, whereas relative peak power was worse in overweight and obese adolescents (p<0.001). Multiple regression analysis revealed that 66.3% of the variance in CMJ and 70.0% of the variance in 20-m sprint may be predicted by gender, body fat percentage, peak force and power. In 13.6% of the participants, limb asymmetries above 15% were detected when limb symmetry index (LSI) was calculated using peak force as underlying factor, whereas only 4.5% had asymmetries in power production between left and right leg. LSIpower was higher in obese when compared to underweight children (p = 0.040). CONCLUSIONS: Findings of variations in peak force and power between body composition categories, with obese subjects having lowest performance scores, particularly when results are expressed in relation to body mass. Most importantly, a slightly higher LSI was detected among obese adolescents adding to the deleterious effects of childhood obesity on health.