Effects of a "5 + 2" dietary management model on body composition and behavioral modification in Chinese children with obesity: a prospective, non-randomized controlled trial.

INTRODUCTION: Continuous energy restriction may be associated with poor adherence and a risk of muscle mass loss in pediatric obesity management. This study evaluated the effects of a structured "5 + 2" dietary management model-cycling 5 weekdays of calorie-restricted diet with 2 weekend days of high-protein diet-supported by standardized supplements and professional supervision. METHODS: In this prospective, non-randomized controlled trial conducted in Shenzhen, China, 84 children with persistent obesity (median age 11.1 years) were enrolled. The intervention group (N = 31) followed an 8-week "5 + 2" protocol with dietitian-led behavioral guidance and satiety-enhancing supplements, followed by a 12-week follow-up period. Controls (N = 53) received conventional weight-loss advice. Propensity score matching was employed to balance baseline cohorts (N = 74; 30 intervention, 44 control). Changes in weight, body composition, metabolic parameters, and behavior were assessed at weeks 8 and 20. RESULTS: At week 8, the intervention group achieved significantly greater weight loss (-1.42 ± 1.73 kg vs. -0.44 ± 1.54 kg, p = 0.015) and body mass index (BMI) standard deviation score (SDS) reduction (-0.21 ± 0.14 vs. -0.11 ± 0.14, p = 0.005) compared to controls. The median behavior score in the intervention group improved significantly from 66.0 to 82.0 (p < 0.001), with marked increases in self-weighing frequency and physical activity. At the 20-week follow-up (post-summer break), the intervention group maintained greater reductions in body fat mass (-1.42 ± 3.41 vs. +1.84 ± 3.67 kg, p < 0.001) and greater skeletal muscle gain (3.90 ± 3.46 vs. 2.21 ± 2.36 kg, p = 0.031) than the control group, with significantly lower fat mass index (FMI) Z-scores and higher muscle mass index (MMI) Z-scores. Linear regression identified boys (β = -0.758, p = 0.015), older children (β = -0.240, p = 0.003) and children with higher baseline adherence (β = -0.356, p = 0.004) as key predictors for BMI SDS reduction. CONCLUSION: The "5 + 2" dietary management model was associated with favorable changes in body composition and health-related behaviors in children with obesity and may represent a practical dietary management strategy.