Study on the Isochronous Substitution Effect of 24-hour Activity Behaviors on Metabolic Syndrome in Adolescents

Background The onset of metabolic syndrome (MS) is becoming younger, and the incidence of MS in adolescents is annually increasing. The 24-hour activity behaviors consist of physical activity (PA), sedentary behavior (SB), and sleep (SLP). The substitution benefits generated by the mutual substitution of activity behaviors are of great significance to the prevention and control of adolescent MS. Objective To explore the substitution benefits of redistributing between SB, the Low Intensity Physical Activity (LPA), Moderate-to-High Intensity Physical Activity (MVPA), and SLP on the risk factors of adolescent MS based on the component isochronous substitution model. Methods From September 2022 to June 2023, 181 subjects aged 12-15 years old from Tianjin, China were randomly recruited, including 85 males and 96 females. SB, LPA, MVPA, SLP of subjects were collected using a 3D accelerometer. The height, body mass, and waist circumference (WC), as well as blood pressure after 15 minutes of rest were recorded. Triglycerides (TG), high-density lipoprotein cholesterol(HDL-C), and blood glucose (GLU) were examined using a fully automated biochemical analyzer and reagent kits. A component equal time substitution model was performed, and 15-minute substitution benefits and continuous substitution at 5-minute intervals were conducted. Results The time of SLP, SB, LPA, and MVPA of subjects were (586.5±66.2) min, (571.2±90.8) min, (233.8±67.2) min, and (49.5±17.8) min, respectively. With the increased MVPA activity time by 15 minutes, the standardized waist circumference decreased by 0.16-0.20 units, the standardized systolic blood pressure (SBP) decreased by 0.12-0.24 units, the standardized diastolic blood pressure (DBP) decreased by 0.18-0.29 units, the standardized blood glucose decreased by 0.03-0.10 units, the standardized TG decreased by 0.02-0.09 units, and the standardized HDL-C increased by 0.05-0.07 units. The utility generated by MVPA replacing SB was superior to the utility generated by MVPA replacing SLP, followed by the utility generated by MVPA replacing LPA. When the MVPA activity time increased by 60 minutes, the standardized waist circumference decreased by 0.02-0.62 units, standardized SBP decreased by 0.06-0.49 units, standardized DBP decreased by 0.08-0.64 units, standardized TG decreased by 0.01-0.14 units, standardized HDL-C increased by 0.03-0.23 units, and standardized blood glucose decreased by 0.01-0.12 units. Conclusion Changes in 24-hour activity behaviors have significant effects on waist circumference, SBP, DBP, blood glucose, TG, and HDL-C in adolescents, with MVPA replacing SB producing the greatest substitution benefit. MVPA is irreplaceable, and the negative benefits generated by other activities replacing MVPA far outweigh the positive benefits generated by MVPA replacing other activities.