Effects of a Combined Exercise and Dietary Intervention on Body Composition and RMR in Obese Children

Abstract

Purpose

Resting metabolic rate (RMR) is a key indicator for weight loss, weight control, and weight regain in children with obesity. This study explores the dose-response relationship between changes in resting metabolic rate and body composition in an intervention for obese children.

Methods

Fifty elementary students with obesity (10–11 years old) were randomly assigned to one experimental group and control group. All the participants participated in a daily 45-min physical education class and a 60-min physical education extracurricular activities recommended by the government. The participants in experimental group also participated in an eight-week combined intervention program including 60 min/day of resistance and aerobic training with standardized dietary intake. Weight was measured daily, body composition weekly, and RMR pre-, mid-, and post-intervention. During the experiment period, obese children wore an ActiGraph GT3X device to measure energy expenditure from physical activity (AEE) and physical activity level (PAL) to adjust dietary intake (EI). At the same time, the Bouchard Physical Activity Diaries (PA diaries) questionnaire was distributed to collect the missing data to ensure the accuracy and objectivity of the data. Generalized estimation equations were used to analyze the effects of body weight and composition changes on RMR.

Results

After 8 weeks of exercise and dietary intervention, the weight changes have no statistically significant difference (P > 0.05). The body fat percentage decreased from 38.5% to 35.2%, while the skeletal muscle mass proportion increased from 32.3% to 34.1%. The intervention effect on the relative value of RMR (kcal/h/kg) was −0.137 kcal/hour/kg. The relationship between body composition and RMR was significant only when fat reduction exceeded 4.5 kg (P<0.01), showing a positive correlation between skeletal muscle increases of 0–4 kg and RMR changes (β = 0.226).

Conclusion

The 8-week combined intervention effectively reduced body weight and altered body composition. This study provides a feasible and effective exercise and diet plan for weight loss and fat reduction. A critical threshold of 4.5 kg fat loss was identified: skeletal muscle mass increases only positively influenced RMR above this threshold. This threshold appears crucial for metabolic adaptation of the 10–11 years old obese children. It shows the importance of monitoring RMR in relation to body weight and composition during fat loss.

Keywords

Resting metabolic rate / Weight / Body composition / Children / Obesity

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Funding

the Academic Research Projects of Beijing Union University(No. JK202314)

the National Science and Technology Innovation 2030, Noncommunicable Chronic Diseases-National Science and Technology Major Project (No. 2023ZD0508500, 2023ZD0508502)

RIGHTS & PERMISSIONS

Beijing Sport University