Smaller weight changes in standardized body mass index in response to treatment as weight classification increases

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% female) between the ages of 9 and 14 (mean = 12.0, standard deviation = 0.7). All participants were classified as overweight, 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, η_p² = .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.