The purpose of the present study was to investigate the influence of the body mass reduction on functional stability in young obese women based on the anterior LOS test. To the authors' best knowledge, this is the first study that compared the ability to control the center of gravity (COG) during the anterior LOS test in obese individuals before and after the weight-loss program. The study results suggest that the weight-loss program, which caused body mass reduction equal to or greater than 5% of the initial body mass and noteworthy changes in the body composition also showed a significant influence on motor behavior and postural control of the women.
In this study, the young obese women after the three-month weight-loss program (that included reduced calories diet and physical activity) demonstrated higher COP maximal velocities during the transition from standing to maximal forward-leaning as well as during maintaining the maximal forward-leaning position. This indicates that after losing weight and improving physical condition, the women were able to perform the task of a dynamic leaning forward faster. Additionally, their body swayed faster during static maintenance of the maximal forward-leaning.
As previous studies showed, a decrease in the COP velocity in the anterior LOS test in the obese compared to that of people with normal body mass indicated a limitation of their postural control [23, 24]. Therefore, increasing the speed of voluntary movement (the dynamic leaning forward) as the result of the weight loss program can be interpreted as an indicator of improved postural control.
Body mass, as well as mass distribution, are key determinants of postural control [6, 28]. It has been shown that in static conditions of quiet standing, young obese women swaying slower due to increased body inertia .This makes their posture more sedate and less sensitive to disturbances. For this reason, obese individuals also slow down their movements to maintain stability during their daily lives  Consequently, obese individuals due to reduced mobility may be at higher risk of falling.
Based on the presented results the authors of this study suggest that the weight reduction created new biomechanical conditions in young obese women.
These new conditions enabled the women for faster transfer from standing to maximal forward-leaning position (phase II of the LOS test). Firstly, less body mass means less body inertia and better movement control; secondly, it means a more advantageous ratio of muscle strength to body mass (as a result of fat loss), and reduced energy expenditure related to movement control. In addition, it should be taken into account that the weight loss program included recommendations to increase physical activity that could have also increased the efficiency of muscle work .
The present study results also indicate that after the three-month weight loss program the obese women swayed faster while maintaining the maximal forward-leaning position (phase III of the LOS test). The faster sway under these challenging static conditions may suggest greater mobility that may give the women the opportunity to perform a defensive move in a shorter time (quickly), i.e. taking a step (see the Nashner’s step strategy; ) in case of a risk of losing balance. However, this study additionally indicates that the effect of losing weight as faster body sway during maintaining maximal forward-leaning position concerned the medial-lateral postural control. This may be related to the possible reduction of the women’s base of support after losing weight. It has been suggested that in standing position, obese individuals adapt to increased body mass by increasing their base of support [32, 33]. This adaptational mechanism may additionally lead to decreased medial-lateral postural sway [11, 14] because ankle joint mobility in the frontal plane is reduced when standing widely [34, 35]. It is, therefore, possible that the young obese female participants of this study used a more narrow stance after the reduction of body mass (and thigh circumference) what additionally increased the velocity of sway in the medial-lateral direction. In this experiment, the subject’s base of support was not measured, which is undoubtedly a limitation of the study.
On the other hand, this study indicates that the obese women’s functional stability that was assessed under visual deprivation conditions was unchanged despite the weight loss program. Perhaps further continuation of reduced calories diet and physical activity would have been necessary to influence their postural control under these more challenging conditions (mean BMI of the women reduced from 36 to 32 after the three-month weight loss program, so it was still far from normal).
This research also indicates that the anterior stability limit (the range of leaning and stability range) did not change in the young obese women after participation in the weight loss program. Possibly, the women’s anterior stability limit was intact before their weight loss because of their young age and lack of serious structural and/or medical consequences that are typical for long-lasting obesity. Earlier studies found reduced limits of stability in older obese women  and women with morbid obesity only .