To investigate the health benefits of 24-hour activity behavioral changes on the physical shape and cardiorespiratory endurance of middle school students with central obesity, so as to provide a basis for improving the health status of middle school students with central obesity.

From October to December 2022, a total of 362 middle school students with central obesity were recruited from 4 middle schools (2 senior high schools and 2 junior high schools) in Dalian by using the random number table method. The 24-hour activity behavior was understood using the International Physical Activity Questionnaire short form and Pittsburgh Sleep Quality Index. The height, weight, waist circumference, body fat percentage, lung capacity, heart function index, maximum oxygen uptake (VO_2max) of the subjects were measured, and body mass index (BMI) and waist-to-height ratio (WHtR) were calculated. Physical shape and cardiorespiratory endurance indicators were normalized, and the component regression was used to explore the correlation between 24-hour activity behavior and physical shape, as well as cardiorespiratory endurance; finally, an isochronous replacement model was established.

The results of the component regression showed that sleep of the participants was positively correlated with BMI, waist circumference, and WHtR (β=2.35, 5.21, 0.01); and sedentary behavior (SB) was negatively correlated with lung capacity and VO_2max (β=-392.45, -1.01), and positively correlated with BMI, waist circumference, WHtR, body fat percentage and cardiac function index (β=4.67, 5.10, 0.14, 3.53, 0.29) (P < 0.05). Low physical activity (LPA) was negatively correlated with BMI, WHtR, body fat percentage and cardiac function index (β=-2.03, -3.70, -0.82), and positively correlated with lung capacity and VO_2max (β=322.23, 0.50) (P < 0.05). Moderate-to-vigorous physical activity (MVPA) had a negative correlation with BMI, waist circumference, WHtR, body fat percentage and heart function index (β=-0.48, -1.20, -0.20, -4.53, -1.12), and a positive correlation with lung capacity and VO_2max (β=393.13, 1.51) (P < 0.05). Increasing MVPA for 30 minutes while reducing SB resulted in a decrease of 0.17-2.05 units in BMI, waist circumference, WHtR, body fat percentage and heart function index, and an increase of 0.38-0.43 units in lung capacity and VO_2max (P < 0.05). When MVPA was replaced by SB, the negative benefits were the greatest, with BMI, waist circumference, WHtR, body fat percentage and heart function index increasing by 0.23-3.06 units (P < 0.05).

Shifts in the 24-hour behavior pattern among obese middle school students may result in significant health benefits. Increasing MVPA by 30 minutes per day while reducing SB can reduce waist circumference, WHtR and body fat percentage, while also improve cardiorespiratory endurance.