ORIGINAL ARTICLE Reducing weight increases postural stability in obese and morbid obese men N Teasdale 1 , O Hue 1 , J Marcotte 1 , F Berrigan 1 , M Simoneau 1 , J Dore ´ 1 , P Marceau 2,3 , S Marceau 2,3 and A Tremblay 1 1 Faculty of Medicine, Department of Social and Preventive Medicine, Laval University, Que´bec, Canada; 2 Faculty of Medicine, Department of Surgery, Laval University, Que´bec, Canada and 3 Department of General Surgery, Laval Hospital, Que´bec,Canada 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. International Journal of Obesity (2007) 31, 153–160. doi:10.1038/sj.ijo.0803360; published online 9 May 2006 Keywords: weight loss; posture; balance control; postural stability Introduction Overweight and obesity are significantly associated with an endless list of diseases such as diabetes, high blood pressure, chronic heart diseases, dyslipidemia, endothelial dysfunc- tion, stroke, cancer (endometrial, breast, prostate and colon cancer), osteoarthritis, sleep apnea and respiratory pro- blems. 1–8 Also there are evidences to suggest that an increased body fat mass decreases postural stability and increases the odds of falling, particularly when combined with low muscle mass. Owusu et al. 9 reported that hip and wrist fractures among 43 053 men aged 40–75 years was increased depending on waist circumference and waist-to- hip ratio. Four studies with obese boys also suggest that obesity imposes added constraints on the postural control system. Petti et al. 10 examined the relationship between obesity and traumatic dental injuries in a study population of 938 school children aged 6–11 years. They reported that more obese children suffer from traumatic accidents to anterior teeth than non-obese children. Goulding et al. 11 reported that in obese boys aged 10–21 there was a significant relationship between body weight, body mass index, percentage of fat and total fat mass and a clinical balance score (Bruininks–Oseretsky). Obese boys also showed greater sway areas and variability in the medial/lateral direction when compared with non-obese prepubertal boys. 12 Altogether, these studies support the view that overweight can yield poorer balance. More recently, Bernard et al. 13 reported similar results in obese teenagers but only when the postural control was stressed by adding a foam surface. Adding a foam surface presumably perturbs the lower limbs somatosensory information and requires a greater reliance on the remaining sensory systems. They Received 12 December 2005; revised 14 March 2006; accepted 15 March 2006; published online 9 May 2006 Correspondence: Professor N Teasdale, Faculty of Medicine, Department of Social and Preventive Medicine, Division of kinesiology, PEPS, Laval Universite ´, Sainte-Foy, Que ´bec, Canada, G1K 7P4. E-mail: Normand.Teasdale@kin.msp.ulaval.ca International Journal of Obesity (2007) 31, 153–160 & 2007 Nature Publishing Group All rights reserved 0307-0565/07 $30.00 www.nature.com/ijo