No abstract

Objective: To investigate the effect of weight loss on balance control in obese and morbid obese men. Methods: In a longitudinal and clinical intervention study, postural stability was measured with a force platform before and after weight loss in men. Weight loss was obtained in obese men (mean body mass index (BMI) ¼ 33.0 kg/m 2 ) by hypocaloric diet until resistance and in morbid obese men (mean BMI ¼ 50.5 kg/m 2 ) by bariatric surgery. Morbid obese men were tested before surgery, and 3 and 12 months after surgery when they had lost 20 and nearly 50% of initial body weight, respectively. Normal weight individuals (mean BMI ¼ 22.7 kg/m 2 ) were tested twice within a 6-to 12-month period to serve as control. Body fatness and fat distribution measures, and posturographic parameters of the center of foot pressure (CP) along the antero-posterior and medio-lateral axes for conditions with and without vision were performed in all subjects. Results: Weight loss averaged 12.3 kg after dieting and 71.3 kg after surgery. Body weight remained unchanged in the control group. After weight loss, nearly all measures of postural stability were improved with and without vision (i.e., CP speed and range in antero-posterior and medio-lateral axes). A strong linear relationship was observed between weight loss and improvement in balance control measured from CP speed (adjusted R 2 ¼ 0.65, Po0.001). Conclusion: Weight loss improves balance control in obese men and the extent of the improvement is directly related to the amount of weight loss. This should decrease the habitual greater risk of falling observed in obese individuals.

Introduction: Obesity yields a decreased postural stability. The potentially negative impact of obesity on the control of upper limb movements, however, has not been documented. This study sought to examine if obesity imposes an additional balance control constraint limiting the speed and accuracy with which an upper limb goal-directed movement performed from an upright standing position can be executed. Method: Eight healthy lean subjects (body mass index (BMI) between 20.9 and 25.0 kg/m 2 ) and nine healthy obese subjects (BMI between 30.5 and 48.6 kg/m 2 ) pointed to a target located in front of them from an upright standing posture. The task was to aim at the target as fast and as precisely as possible after an auditory signal. The difficulty of the task was varied by using different target sizes (0.5, 1.0, 2.5 and 5.0 cm width). Hand movement time (MT) and velocity profiles were measured to quantify the aiming. Centre of pressure and segmental kinematics were analysed to document postural stability. Results: When aiming, the forward centre of pressure (CP) displacement was greater for the obese group than for the normal BMI group (4.6 and 1.9 cm, respectively). For the obese group, a decrease in the target size was associated with an increase in backward CP displacement and CP peak speed whereas for the normal BMI group backward CP displacements and CP peak speed were about the same across all target sizes. Obese participants aimed at the target moving their whole body forward whereas the normal BMI subjects predominantly made an elbow extension and shoulder flexion. For both groups, MT increased with a decreasing target size. Compare to the normal BMI group, this effect was exacerbated for the obese group. For the two smallest targets, movements were on average 115 and 145 ms slower for the obese than for the normal BMI group suggesting that obesity added a balance constraint and limited the speed with which an accurate movement could be done. Summary: Obesity, because of its effects on the control of balance, also imposes constraints on goal-directed movements. From a clinical perspective, obese individuals might be less efficient and more at risk of injuries than normal weight individuals in a large number of work tasks and daily activities requiring upper limb movements performed from an upright standing position.

Plasma organochlorine concentration increases with weight loss and is related to the magnitude. Future research will have to determine if: 1) this pollutant concentration remains elevated over time and 2) there are long-term effects of this high concentration on health.

Despite a large force loss, particularly for the lower limbs in morbidly obese individuals after surgery, this loss is relatively well tolerated because the relation between force and body weight is even improved and the ability to maintain that force is preserved.