Effects of Compositional Isotemporal Substitutions of 24 Hours Activity Behaviors on Novel Obesity Indicators in College Students.

Objective To explore the effects of time reallocation among moderate-to-vigorous physical activity(MVPA),light physical activity(LPA),sedentary behavior(SB),and sleep on a body shape index(ABSI),body roundness index(BRI),conicity index(CI),and relative fat mass(RFM)of college students by the compositional isotemporal substitution method,thus providing measures for alleviating the obesity problem of college students. Methods Two hundred and ten college students(111 males and 99 females)aged 18-22 years old were recruited from Tianjin University of Science and Technology from April to June in 2023.Three-dimensional acceleration sensors were used to collect data of MVPA,LPA,SB,and sleep of college students.The body height,body weight,and waist circumference were measured,and four novel obesity indicators(ABSI,BRI,CI,and RFM)were calculated.The effects of substituting each activity behavior for 15 min on the obesity indicators were predicted,and the dose-effect relationship was explored at intervals of 5 min from -30 to 30 min.Results MVPA was negatively correlated with ABSI(=-0.03,=0.001),BRI(=-0.27,=0.049),CI(=-0.10,=0.001),and RFM(=-9.95,=0.004).LPA was negatively correlated with CI(=-0.05,=0.011)and RFM(=-8.74,=0.007).Neither SB nor sleep had correlations with ABSI,BRI,CI,and RFM.The results of 15 min isotemporal substitutions showed that increasing the MVPA time decreased the ABSI,BRI,CI,and RFM by 0.006-0.008,0.306-0.393,0.162-0.205,and 2.468-2.897,respectively.Decreasing the MVPA time increased the ABSI,BRI,CI,and RFM by 0.012-0.014,0.548-0.632,0.286-0.328,and 4.358-4.748,respectively.In the dose-effect relationship from -30 min to 30 min,MVPA was irreplaceable,and the negative benefits from substituting MVPA for other activity behaviors were much greater than the positive benefits from substituting MVPA for other activity behaviors.Conclusions Future research should take 24 hours activity behaviors as a whole.Increasing the time spent on MVPA and LPA and decreasing the time spent on SB is one of the effective ways to alleviate the obesity problem among college students.