Smaller Weight Changes in Standardized Body Mass Index in Response to Treatment as Weight Classification Increases Craig A. Johnston, PhD, Chermaine Tyler, PhD, Jennette L. Palcic, PhD, Sandra A. Stansberry, BA, Martina R. Gallagher, PhD, RN, and John P. Foreyt, PhD Objectives To compare the differential efficacy of a weight loss program for Mexican-American children who are overweight, obese, and severely obese. Study design Study participants were enrolled in an intensive weight loss intervention aimed at improving eating and physical activity behaviors with behavior modification strategies. Participants included 212 children (45% fe- male) between the ages of 9 and 14 (mean = 12.0, standard deviation = 0.7). All participants were classified as over- weight, obese, or severely obese. Results Repeated measures analyses revealed that children in the overweight, obese, and severely obese weight categories differed significantly in standardized body mass index (zBMI) decreases at baseline, 3, 6, and 12 months (F = 4.57, P < .01, h p 2 = .06). Follow-up paired samples t tests showed a significant change in zBMI from baseline to 3 and 6 months for children in the overweight, obese, and severely obese weight categories. However, at 12 months only the overweight and obese students continued to show significant improvement from baseline in zBMI. Conclusions These findings suggest that an intensive behavioral weight loss intervention that has demonstrated efficacy for decreasing zBMI may have incrementally smaller effects for children as weight classification increases. (J Pediatr 2011;158:624-7). C hildhood overweight has increased in prevalence nearly threefold since 1980. 1 Although studies suggest the increase in prevalence among children may be slowing, the heaviest boys are becoming even heavier. 1 This is particularly problem- atic for ethnic minorities. These groups not only have the highest rates of overweight, but they also have the highest rates of associated health problems, such as type 2 diabetes, fatty liver disease, hypertension, and hyperlipidemia. 2 Among ethnic minorities, Hispanic children and adolescents are at the greatest risk for overweight and obesity. 1 Most successful weight management treatments involve multicomponent programs comprised of behavior modification, nutrition education, and physical activity. 3 However, studies often have stringent inclusion and exclusion criteria that may ex- clude children with severe obesity (body mass index [BMI] $ 99th percentile) from participation. 4 This prevents an assessment of their potential for success in these programs. Furthermore, studies that include severely obese participants often result in only modest weight loss. 5 This study investigated the differential efficacy of a weight loss program for Mexican-American children who are overweight, obese, and severely obese. We hypothesized that children who were severely obese would demonstrate less benefit from the intervention compared with children classified as overweight and obese. Methods This analysis combines the results of 5 studies with similar designs which evaluated the efficacy of an intensive weight loss in- tervention with Mexican-American children. Previous evaluations of the intensive intervention demonstrated that children re- ceiving the intervention significantly reduced their standardized body mass index (zBMI) compared with children in a self-help condition. 6-8 The interventions were conducted at a charter school in Houston, Texas, that serves an urban student population that is 95% Mexican-American. All studies were approved by the institutional re- view board for human subjects at Baylor College of Medicine. A total of 357 overweight and obese students were randomized after baseline measurements to either an instructor-led intervention (ILI) (n = 212) condition or a self help (n = 145) condition. Only children in the ILI condition are included in the following analyses to determine differential treatment outcomes for chil- dren in different weight classifications. From the USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics-Nutrition (C.J., C.T., J.P., S.S., J.F.); the Department of Medicine (J.F.), Baylor College of Medicine; and the University of Texas Health Science Center at Houston School of Nursing (M.G.), Houston, TX Supported by a grant from the United States Department of Agriculture (ARS 2533759358). The funding source played no role in study design, collection, analysis, or interpretation of data, the writing of the report or the decision to submit for publication. There are no conflicts of interest to disclose. 0022-3476/$ - see front matter. Copyright ª 2011 Mosby Inc. All rights reserved. 10.1016/j.jpeds.2010.09.049 BMI Body mass index ILI Instructor-led intervention ITT Intention-to-treat zBMI Standardized body mass index 624