Influencing Factors And Physical Activity Intervention Of Resting Metabolic Rate For Tibetan And Han Adolescents In Plateau Area

In the total energy consumption of human body,resting energy consumption accounts for 60%-70%.Accurate measurement of resting metabolic rate(RMR)is of great significance to guide reasonable energy intake.Among many RMR measurement methods,formula inference method is widely used in large-scale population measurement because of its fast and simple characteristics.However,the widely used RMR inference formula at present mostly takes European and American people as research samples,which has racial differences with Chinese people.In addition,the low oxygen environment in Tibet will lead to higher RMR than that in plain areas,and the existing speculative formula may not be applicable to Tibetan adolescents.In addition to accurately assessing the level of RMR,in order to formulate more targeted interventions,it is also necessary to further understand the differences and influencing factors of RMR in age,gender,ethnic group and nutritional status.Among the factors affecting RMR,physical activity is a special one.On the one hand,physical activity is not only directly related to RMR,but also may affect RMR indirectly by changing body composition.On the other hand,there is a covariance among components of physical activity,so it is necessary to use isotemporal substitution model to explore the relationship between the physical activity and RMR.Based on the understanding of the relationship between physical activity and RMR,further experimental studies are needed to verify the effect of physical activity intervention in order to better guide practice.Based on the above background,this study uses the method of stratified cluster random sampling to measure RMR,body composition and physical activity of 13-18-year-old adolescents in Nyingchi,Qamdo,Lhasa and Naqu in Tibet Autonomous Region from August 2019 to December 2020.It intends to solve the following four problems:(1)Develop RMR predictive equations suitable for Tibetan and Han adolescents in plateau area;(2)To explore the influencing factors of RMR among Tibetan and Han adolescents(3)To explore the relationship between physical activity and RMR of Tibetan and Han adolescents;(4)Further verify the impact of physical activity intervention on RMR and whether there are ethnic differences.Through the research on the above problems,we hope to provide reference for promoting the physical health of Tibet Autonomous Region adolescents in theory and practice.It includes the following four studies:Study 1:The predictive equations of resting metabolic rate for Tibetan and Han adolescents in plateau areaObjective:To develop RMR equations suitable for Tibetan and Han adolescents in plateau area.Methods:593 Tibetan and Han adolescents aged 13?18 in Lhasa were randomly selected as the subjects.Indirect calorimetry was used to measure RMR,and body composition was measured by electrical resistance.Stepwise regression,Perason correlation analysis,paired sample t test,bias rate method and Bland-Altman method were used to analyze the data.Results:(1)the R~2 of the predictive equations with FFM as the independent variable were greater than that of the predictive equations with height or weight as the independent variable,and the R~2of the age segmentation equation was greater than that of the age combination equation.After the gender was included,the R~2 of the predictive equations became larger;(2)Considering comprehensively,the effectiveness of model8 and model 10 in this study is good.In the above two models,the correlation between the predicted value and the measured value is higher than the existing equations(Tibetan:r_{model 8}=0.78,r_{model 10}=0.82;Han:r_{model 8}=0.86,r_{model 10}=0.78);The mean of the difference(MD)between the predicted value and the measured value is lower than the existing equations(Tibetan:MD_{model 8}=0.1 kcal/d,MD_{model 10}=0.2 kcal/d;Han:MD_{model 8}=-0.8 kcal/d,MD_{model 10}=2.3 kcal/d);The accuracy is higher than the existing equations(Tibetan:Accuracy_{model 8}=80.0%,Accuracy_{model 10}=67.3%;Han:Accuracy_{model 8}=70.6%,Accuracy_{model 10}=72.3%);Root mean square error(RMSE)is lower than the existing equations(Tibetan:RMSE_{model 8}=221.0 kcal/d;RMSE_model10=219.4 kcal/d;Han:RMSEmodel 8=248.6 kcal/d;RMSEmodel ₁₀=209.5 kcal/d).Summary:In this study,the age segmentation predictive equations with FFM,gender and age as independent variables can be used to evaluate the RMR of Tibetan and Han adolescents on the plateau.The specific equations are:Tibetan:13-15 years old,RMR(kcal/d)=50.1×FFM(kg)-202.8×Gender(Girl:0;Boy:1)-72.1×Age+930.3,(R~2=0.63);16-18 years old,RMR(kcal/d)=58.4×FFM(kg)-441.1×Gender(Girl:0;Boy:1)-702.2,(R~2=0.63)Han:13-15 years old,RMR(kcal/d)=65.8×FFM(kg)-321.3×Gender(Girl:0;Boy:1)-772.3,(R~2=0.64);16-18 years old,RMR(kcal/d)=51.4×FFM(kg)-234.5×Gender(Girl:0;Boy:1)-49.4×Age+247.6,(R~2=0.68)Study 2:The difference of resting metabolic rate between Tibetan and Han adolescents in plateau area and its influencing factorsObjective:A large epidemiological survey was conducted using the predictive equations of Study 1 to explore the influencing factors of RMR among Tibetan and Han adolescents in plateau area,and to provide basis for formulating more targeted intervention measures.Methods:2806 Tibetan and Han adolescents were selected by stratified cluster random sampling in Nyingchi,Qamdo,Lhasa and Naqu.The sleep,diet and psychology of all samples were investigated by questionnaire.1636 adolescents were randomly selected and their physical activities were measured by accelerometer.RMR was calculated using the predictive equations in Study 1.The ratio method was used to adjust RMR:RMR_adj(adjusted RMR)=RMR/FFM.Data were analyzed by LMS method,one-way analysis of variance,covariance analysis and calculation of effect size.Results:(1)the mean RMR of Tibetan boys and girls were 1834.0 kcal/d and1618.0 kcal/d,and that of Han were 1872.0 kcal/d and 1631.3 kcal/d,respectively.The mean RMR_adj of Tibetan male and female was 39.0 kcal/d/kg and 43.4 kcal/d/kg,respectively,and that of Han was 39.1 kcal/d/kg and 42.6 kcal/d/kg,respectively.In terms of gender difference,the RMR of Tibetan and Han boys was higher than that of female students,while the RMR_adj of male students was lower than that of female students(P<0.001).The age difference of RMR and RMR_adj between Tibetan and Han male and female students was statistically significant(P<0.001).In terms of ethnic differences,the RMR and RMR_adj of Tibetan and Han boys were higher and lower at the age of 15(P<0.001).There was no significant difference in RMR between Tibetan and Han girls,while RMR_adj of Tibetan girls was higher than that of Han girls(P<0.001).The differences of RMR and RMR_adj in different nutritional status between Tibetan and Han male and female students were statistically significant(P<0.001).In terms of altitude difference,RMR_adj-Z of Tibetan adolescents in high altitude was the highest(3.9),followed by Han adolescents in high altitude(3.0)and Han adolescents in plain area(2.2),with statistical significance(P<0.001).(2)RMR and RMR_adj are negatively correlated with sedentary behavior(SB)(B values were-0.21 and-0.01,P<0.001).Light physical activity(LPA)(B values were 1.03 and 0.02,P<0.05),moderate-to-vigorous physical activity(MVPA)(B values were 1.32 and 0.04,P<0.001)were positively correlated.RMR and RMR_adj were negatively correlated with LPA(B values were-1.14 and-0.03,P<0.001),and positively correlated with MVPA(B values were 3.53 and 0.10,P<0.001).Sleep,diet and psychology were not statistically significant with RMR and RMR_adj.Summary:(1)There are differences in gender,age,ethnicity and nutritional status of RMR and RMR_adj between Tibetan and Han adolescents;RMR_adj-Z of Tibetan adolescents in high altitude was the highest,followed by Han adolescents in high altitude and Han adolescents in plain area.(2)Physical activity was closely related to RMR and RMR_adj of Tibetan and Han adolescents,while sleep,diet and psychology were irrelevant.Study 3:The relationship between physical activity and resting metabolic rate of Tibetan and Han adolescents in plateau areaObjective:On the basis of study 2,the relationship between physical activity and RMR of Tibetan and Han adolescents was further explored:(1)To examine whether FFM plays a mediating role in the relationship between physical activity and RMR;(2)On the basis of determining the direct relationship between physical activity and RMR,the relationship between isotemporal substitution of physical activity variables and RMR was examined.Methods:A total of 1,636 participants were selected from study 2 for physical activity testing,and a total of 1,581 participants were eventually included in the study,excluding 55 participants who failed to wear the accelerometer.In the mediation effect analysis:First,examine the relationship between physical activity and RMR,and proceed to the next step if it is significant.Second,examine the relationship between physical activity and FFM and FFM and RMR.If they are all significant,FFM plays at least a partial mediating role.Third,the significance of FFM was examined when FFM was included in the relationship between physical activity and RMR.If significant,FFM plays a partial mediating role;If not significant,FFM plays a complete mediating role.In isotemporal substitution analysis,3 models(excluding SB,LPA and MVPA respectively)were established with 10 minutes as isotemporal substitution duration to evaluate the relationship between physical activity and mutual substitution and RMR.Results:(1)FFM did not play a mediating role in the relationship between SB and RMR in Tibetan and Han boys,but played a partial mediating role in female students(Tibetan:B=0.91,P<0.001;Han:B=0.87,P<0.001);Except Tibetan boys,FFM played a completely mediating role in the relationship between LPA and RMR(Tibetan girls:B=0.93,P<0.001;Han boys:B=0.97,P<0.001;Han girls:B=0.90,P<0.001);FFM played a partial mediating role in the relationship between MVPA and RMR in Tibetan and Han boys and girls(B value ranged from 0.88 to 0.96,P<0.001).(2)MVPA isotemporal substitution of SB(B value ranged from 11.23 to 38.97,P<0.01)or LPA(B value ranged from 24.05 to 47.43,P<0.001)for Tibetan and Han boys and girls;except Tibetan boys)was positively correlated with RMR.Summary:(1)SB and MVPA are not only directly related to RMR,but also indirectly related to RMR through FFM.LPA is indirectly related to RMR mainly through FFM.(2)MVPA isotemporal substitution of SB or LPA was positively correlated with RMR.Study 4:The effect of physical activity intervention on resting metabolism of Tibetan and Han adolescents in plateau areaObjective:On the basis of study 2,verify whether increasing MVPA and reducing SB can positively affect resting metabolism of Tibetan and Han adolescents,and to investigate whether there is ethnic difference in the impact of physical activity intervention on resting metabolism.Methods:59 subjects(29 Tibetan and 30 Han)in the experimental group and 55subjects(27 Tibetan and 28 Han)in the control group were randomly selected from the Study 3.The experimental group received 60 minutes of physical activity intervention3 times a week for 12 weeks.The control group had normal self-study.Body composition,respiratory function and RMR tests were performed before and after the intervention.Paired sample t test and one-way ANOVA were used to compare and calculate the effect size.Results:(1)The difference of FFM before and after intervention was 0.83 kg for Tibetan girls,1.00 kg for Han boys and 0.58 kg for Han girls,which was higher after intervention than before(P<0.05).The differences of VE/VO₂ and RQ before and after intervention were-3.0 and-0.06 in Tibetan boys and-5.0 and-0.08 in Han boys,respectively,which were lower after intervention than before(P<0.05).The difference of oxygen uptake(VO₂)before and after intervention was 35.7 m L/min for Tibetan boys and 72.7 m L/min for Han boys,which was higher after intervention than before(P<0.05).The differences of RMR,RMR_adj and FAT oxidation percentage before and after intervention were:Tibetan boys 332.9 kcal/d,7.5 kcal/d/kg and 10.2%,Tibetan girls 330.1 kcal/d,7.7 kcal/d/kg and 12.7%,Han boys 535.4 kcal/d,11.0 kcal/d/kg and14%.It was higher after intervention than before(P<0.05).The RMR of Han girls was higher after intervention than before,the difference was 223.1 kcal/d(P<0.05).(2)The weight difference of Tibetan and Han boys before and after intervention was 0.6kg and 1.3 kg,respectively,and the difference was statistically significant(P<0.05).The difference of VO₂/HR of girls before and after intervention was 1.0 m L/min for Tibetan and 0.2 m L/min for Han,with statistically significant difference(P<0.05),while there was no statistically significant difference for other indicators before and after intervention.Summary:(1)Physical activity intervention increased FFM,VO₂,RMR,RMR_adjand FAT%,and decreased VE/VO₂ and RQ;(2)Overall,there were no significant ethnic differences in the effects of physical activity intervention on body composition,resting metabolism and respiratory function.Based on the above studies,the following conclusions can be drawn:(1)In this study,the age segmentation predictive estimations with FFM,gender and age as independent variables can be used to evaluate the RMR of Tibetan and Han adolescents in plateau area.The specific equations are:Tibetan:13-15 years old,RMR(kcal/d)=50.1×FFM(kg)-202.8×Gender(Girl:0;Boy:1)-72.1×Age+930.3,(R~2=0.63);16-18 years old,RMR(kcal/d)=58.4×FFM(kg)-441.1×Gender(Girl:0;Boy:1)-702.2,(R~2=0.63)Han:13-15 years old,RMR(kcal/d)=65.8×FFM(kg)-321.3×Gender(Girl:0;Boy:1)-772.3,(R~2=0.64);16-18 years old,RMR(kcal/d)=51.4×FFM(kg)-234.5×Gender(Girl:0;Boy:1)-49.4×Age+247.6,(R~2=0.68)(2)Gender,age,ethnic group and nutritional status in internal factors and altitude in environmental factors are closely related to RMR;Among the controllable factors,physical activity is significantly associated with RMR,while sleep,diet and psychology are not significantly associated with RMR.(3)SB and MVPA are not only directly related to RMR,but also indirectly related to RMR through FFM.LPA is indirectly related to RMR mainly through FFM.MVPA isotemporal substitution of SB or LPA was positively correlated with RMR.(4)Physical activity intervention promoted the RMR of Tibetan and Han adolescents,but there was no significant ethnic difference.