Objectives: To investigate whether the degree of obesity predicts the efficacy of long-term behavioral treatment and to explore any interaction with age.
Design: A 3-year longitudinal observational study. Obese children were divided into 3 age groups (6-9, 10-13, and 14-16 years) and also into 2 groups (moderately obese, with a body mass index [BMI]-standard deviation [SD] score [or z score] of 1.6 to <3.5, and severely obese, with a BMI-SD score of ≥3.5).
Setting: National Childhood Obesity Center, Stockholm, Sweden.
Participants: Children 6 to 16 years of age who started treatment between 1998 and 2006.
Intervention: Behavioral treatment of obesity.
Main outcome measure: Change in BMI-SD score during 3 years of treatment; a reduction in BMI-SD score of 0.5 units or more was defined as clinically significant.
Results: A total of 643 children (49% female children) met the inclusion criteria. Among the youngest moderately obese children, 44% had a clinically significant reduction in BMI-SD score (mean reduction, -0.4 [95% CI, -0.55 to -0.32]). Treatment was less effective for the older moderately obese children. Twenty percent of children who were 10 to 13 years of age and 8% of children who were 14 to 16 years of age had a reduction in BMI-SD score of 0.5 units or more; 58% of the severely obese young children showed a clinically significant reduction in BMI-SD score (mean reduction, -0.7 [95% CI, -0.80 to -0.54]). The severely obese adolescents showed no change in mean BMI-SD score after 3 years, and 2% experienced clinically significant weight loss. Age was found to be a predictor of a reduction in BMI-SD score (odds ratio, 0.68 units per year [95% CI, 0.60-0.77 units per year]).
Conclusions: Behavioral treatment was successful for severely obese children but had almost no effect on severely obese adolescents.