The study is aimed to examine balance control of slightly obese young adults during quiet stance and during gait initiation with and without crossing an obstacle. Forty-four young subjects were divided in two groups: control (BMI<25 kg/m2 ) and slightly obese (BMI from 25 to 35 kg/m2 ). Center of foot pressure (CoP) and kinematics of fifth lumbar vertebra (L5) were evaluated using a force plate and a motion capture system. During quiet stance with eyes open slightly obese group showed increased mean amplitude and velocity of CoP in anterior-posterior direction compared to normal weight subjects. During unloading phase of gait initiation significantly greater and faster lateral CoP shift was observed in slightly obese group compared to normal weight peers. Presence of an obstacle increased amplitude and velocity of the lateral CoP shift similarly in both groups. No BMI-related differences were found on L5 segment during gait initiation, which may indicate that postural control was already successfully performed in feet (CoP). We have shown that increased CoP parameters values and thus increased postural instability during quiet stance and during unloading phase of gait initiation is present not only in morbidly obese, but already in slightly obese subjects.