Abstract: 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（HDL），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 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 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 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.

Key words: Metabolic syndrome, Adolescent, Physical activity, Sedentary behavior, Waist circumference, Isochronous substitution

摘要： 背景　代谢综合征（MS）的发生逐渐年轻化，青少年MS的发病率逐年增加。24 h活动行为由身体活动（PA）、久坐行为（SB）、睡眠（SLP）构成，活动行为之间相互替代产生的替代效益对于预防与控制青少年MS有重要意义。目的　基于成分等时替代模型探讨SB、低强度身体活动（LPA）、中高强度身体活动（MVPA）、SLP之间重新分配对青少年MS危险因素的替代效益。方法　2022年9月—2023年6月在天津市随机招募12~15岁受试者181名（包括男85名、女96名）。使用三维加速度计采集受试者的SB、LPA、MVPA、SLP；测量受试者的身高、体质量和腰围（WC），安静15 min后测量受试者的血压；使用全自动生化分析仪及试剂盒测量三酰甘油（TG）、高密度脂蛋白（HDL）、血糖（GLU）；建立成分等时替代模型，分别进行15 min的替代效益与以5分钟为间隔的连续替代。结果　受试者SLP时间为（586.5±66.2）min、SB为（571.2±90.8）min、LPA为（233.8±67.2）min、MVPA为（49.5±17.8）min；增加15 min的MVPA活动时间时，标准化腰围将减少0.16~0.20个单位、标准化收缩压将下降0.12~0.24个单位、标准化舒张压将下降0.18~0.29个单位、标准化血糖将下降0.03~0.10个单位、标准化三酰甘油将下降0.02~0.09个单位、标准化高密度脂蛋白将升高0.05~0.07个单位。MVPA替代SB产生的效用>MVPA替代SLP产生的效用>MVPA替代LPA产生的效用；当MVPA时间增加60 min时，标准化腰围降低0.02~0.62个单位、标准化收缩压下降0.06~0.49个单位、标准化舒张压下降0.08~0.64个单位、标准化三酰甘油下降0.01~0.14个单位、标准化高密度脂蛋白升高0.03~0.23个单位、标准化血糖降低0.01~0.12个单位。结论　24 h活动行为的改变对青少年的腰围、收缩压、舒张压、血糖、三酰甘油、高密度脂蛋白均产生明显作用，其中MVPA替代SB能够产生最大的替代效益。MVPA具有不可替代性，其他活动行为替代MVPA产生的负效益远大于MVPA替代其他行为产生的正效益。

关键词: 代谢综合征, 青少年, 身体活动, 久坐生活方式, 腰围, 等时替代