human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Overweight and obesity affects more than 66 % of the adult population and is associated with a variety of chronic diseases . Weight reduction reduces health risks associated with chronic diseases and is therefore encouraged by major health agencies . Guidelines of the National Heart , Lung , and Blood Institute ( NHLBI ) encourage a 10 % reduction in weight , although considerable literature indicates reduction in health risk with 3 % to 5 % reduction in weight . Physical activity ( PA ) is recommended as a component of weight management for prevention of weight gain , for weight loss , and for prevention of weight regain after weight loss . In 2001 , the American College of Sports Medicine ( ACSM ) published a Position St and that recommended a minimum of 150 min wk(-1 ) of moderate-intensity PA for overweight and obese adults to improve health ; however , 200 - 300 min wk(-1 ) was recommended for long-term weight loss . More recent evidence has supported this recommendation and has indicated more PA may be necessary to prevent weight regain after weight loss . To this end , we have reexamined the evidence from 1999 to determine whether there is a level at which PA is effective for prevention of weight gain , for weight loss , and prevention of weight regain . Evidence supports moderate-intensity PA between 150 and 250 min wk(-1 ) to be effective to prevent weight gain .  Moderate-intensity PA between 150 and 250 min wk(-1 ) will provide only modest weight loss . Greater amounts of PA ( > 250 min wk(-1 ) ) have been associated with clinical ly significant weight loss .  Moderate-intensity PA between 150 and 250 min wk(-1 ) will improve weight loss in studies that use moderate diet restriction but not severe diet restriction . Cross-sectional and prospect i ve studies indicate that after weight loss , weight maintenance is improved with PA > 250 min wk(-1 ) . However , no evidence from well- design ed r and omized controlled trials exists to judge the effectiveness of PA for prevention of weight regain after weight loss .  Resistance training does not enhance weight loss but may increase fat-free mass and increase loss of fat mass and is associated with reductions in health risk . Existing evidence indicates that endurance PA or resistance training without weight loss improves health risk . There is inadequate evidence to determine whether PA prevents or attenuates detrimental changes in chronic disease risk during weight gain BACKGROUND The proportion of overweight adolescents has increased , but the behavioral risk factors for overweight youth are not well understood . OBJECTIVE To examine how diet , physical activity , and sedentary behaviors relate to overweight status in adolescents . DESIGN AND SETTING Baseline data from the Patient-Centered Assessment and Counseling for Exercise Plus Nutrition Project , a r and omized controlled trial of adolescents to determine the effects of a clinic-based intervention on physical activity and dietary behaviors . PARTICIPANTS A total of 878 adolescents aged 11 to 15 years , 42 % of whom were from minority background s. MAIN OUTCOME MEASURE Centers for Disease Control and Prevention body mass index-for-age percentiles divided into 2 categories : normal weight ( < 85th percentile ) and at risk for overweight plus overweight ( AR + O ) ( > or=85th percentile ) . RESULTS Overall , 45.7 % of the sample was classified as AR + O with a body mass index for age at the 85th percentile or higher . More girls from minority background s ( 54.8 % ) were AR + O compared with non-Hispanic white girls ( 42 % ) ( chi(2)(1 ) = 7.6 ; P = .006 ) . Bivariate analyses indicated that girls and boys in the AR + O group did fewer minutes per day of vigorous physical activity , consumed fewer total kilojoules per day , and had fewer total grams of fiber per day than those in the normal-weight group . Boys in the AR + O group also did fewer minutes per day of moderate physical activity and watched more minutes per day of television on nonschool days than normal-weight boys . Final multivariate models indicated that independent of socioeconomic status ( as assessed by household education level ) , girls had a greater risk of being AR + O if they were Hispanic or from another minority background ( odds ratio [ OR ] = 1.65 ; 95 % confidence interval [ CI ] , 1.09 - 2.49 ) and a reduced risk of being AR + O as minutes per day of vigorous physical activity increased ( OR = 0.93 ; 95 % CI , 0.89 - 0.97 ) . A low level of vigorous physical activity was the only significant risk factor for boys being AR + O ( OR = 0.92 ; 95 % CI , 0.89 - 0.95 ) . Analyses based on meeting behavioral guidelines supported these findings and showed that failing to meet the 60 min/d moderate to vigorous physical activity guideline was associated with overweight status for both girls and boys . In addition , boys who failed to meet sedentary behavior and dietary fiber guidelines were more likely to be overweight . CONCLUSIONS Of the 7 dietary and physical activity variables examined in this cross-sectional study , insufficient vigorous physical activity was the only risk factor for higher body mass index for adolescent boys and girls . Prospect i ve studies are needed to clarify the relative importance of dietary and physical activity behaviors on overweight in adolescence BACKGROUND It is unclear how moderate and vigorous intensities of physical activity ( PA ) are associated with cardiovascular fitness ( CVF ) and percentage of body fat ( % BF ) in adolescents . OBJECTIVE We tested the hypothesis that vigorous PA , to a greater degree than moderate PA , would be associated with better CVF and lower % BF . DESIGN This was a cross-sectional study of 421 black and white high school students ( x age : 16 y ) .  PA was measured with 5 d of accelerometry and expressed in min/d of moderate or vigorous PA .  CVF was measured with a multistage treadmill test and was expressed as the oxygen consumption at a heart rate of 170 bpm . % BF was measured with dual-energy X-ray absorptiometry . Multiple regressions were used to determine the degree to which variance in CVF and % BF was explained by PA , after control for age , sex , race , and the sex x race interaction . RESULTS A higher index for CVF was associated with higher amounts of moderate and vigorous PA ;  more variance was explained by vigorous than by moderate PA .  Lower % BF was associated with higher amounts of vigorous PA but not with the amount of moderate PA . CONCLUSION Black and white adolescents who engaged in relatively large amounts of free-living vigorous exercise were likely to be relatively fit and lean BACKGROUND Little is known about how the intensity of exercise influences cardiovascular fitness and body composition , especially in obese adolescents . OBJECTIVE Our goal was to determine the effects of physical training intensity on the cardiovascular fitness , percentage of body fat ( % BF ) , and visceral adipose tissue ( VAT ) of obese adolescents . DESIGN Obese 13 - 16-y-olds ( n = 80 ) were assigned to 1 ) biweekly lifestyle education ( LSE ) , 2 ) LSE + moderate-intensity physical training , or 3 ) LSE + high-intensity physical training . The intervention lasted 8 mo . Physical training was offered 5 d/wk , and the target energy expenditure for all subjects in physical training groups was 1047 kJ ( 250 kcal)/session . Cardiovascular fitness was measured with a multistage treadmill test , % BF with dual-energy X-ray absorptiometry , and VAT with magnetic resonance imaging . RESULTS The increase in cardiovascular fitness in the high-intensity physical training group , but not in the moderate-intensity group , was significantly greater than that in the LSE alone group ( P = 0.009 ) ; no other comparisons of the 3 groups were significant . Compared with the LSE alone group , a group composed of subjects in both physical training groups combined who attended training sessions > or=2 d/wk showed favorable changes in cardiovascular fitness ( P < 0.001 ) , % BF ( P = 0.001 ) , and VAT ( P = 0.029 ) . We found no evidence that the high-intensity physical training was more effective than the moderate-intensity physical training in enhancing body composition . CONCLUSIONS The cardiovascular fitness of obese adolescents was significantly improved by physical training , especially high-intensity physical training . The physical training also reduced both visceral and total-body adiposity , but there was no clear effect of the intensity of physical training BACKGROUND Body mass index ( BMI ) during adolescence is predictive of BMI at adult age . However , BMI can not distinguish between lean and fat body mass . Skinfold thickness may be a better predictor of body fatness . OBJECTIVE The objective of this study was to evaluate the relations between BMI and skinfold thickness during adolescence and body fatness during adulthood . DESIGN We included 168 men and 182 women from the Amsterdam Growth and Health Longitudinal Study , a prospect i ve study that conducted 8 measurements of BMI and skinfold thickness between 1976 and 2000 .  BMI and skinfold thickness during adolescence were analyzed in relation to adult body fatness measured at a mean age of 37 y with dual-energy X-ray absorptiometry . RESULTS None of the boys and 1.7 % of the girls were overweight at baseline , whereas the prevalence of high body fatness during adulthood was 29 % in men and 32 % in women . At the ages of 12 - 16 y , skinfold thickness was more strongly associated with adult body fatness than was BMI . Age-specific relative risks for a high level of adult body fatness varied between 2.3 and 4.0 in boys and between 2.1 and 4.3 in girls in the highest versus the lowest tertile of the sum of 4 skinfold thicknesses . For the highest tertile of BMI , the relative risk varied between 0.8 and 2.1 in boys and between 1.3 and 1.8 in girls . CONCLUSION Skinfold thickness during adolescence is a better predictor of high body fatness during adulthood than is BMI during adolescence BACKGROUND It is unclear whether physical activity energy expenditure ( PAEE ) predicts changes in body composition . OBJECTIVE The objective was to describe the independent associations between PAEE and changes in body composition in a population -based cohort . DESIGN This was a prospect i ve population -based study conducted in 739 ( 311 men and 428 women ) healthy middle-aged ( median age : 53.8 y ) whites . The median follow-up was 5.6 y. PAEE ( MJ/d ) was assessed by heart rate monitoring , individually calibrated by using the FLEX heart rate method .  Fat mass ( FM ) and fat-free mass ( FFM ) were assessed by bioimpedance . RESULTS Body weight ( BW ) at follow-up was significantly related to baseline PAEE ( P < 0.05 ) after adjustment for sex , baseline age , FM , FFM , and follow-up time . A significant interaction between PAEE and age ( P = 0.023 ) was observed . After the subjects were stratified ( above and below the median for age ) , BW increased by a mean ( + /-SD ) of 1.7 + /- 5.9 kg ( P < 0.0001 ) in the younger cohort . In this group , follow-up FM was significantly associated with baseline PAEE ( P = 0.036 ) after adjustment for confounders . In the older cohort , BW did not change between baseline and follow-up . In this group , in contrast with the younger population , follow-up BW , FM , and FFM were all significantly and positively associated with baseline PAEE ( P < 0.01 for all ) . CONCLUSIONS Baseline PAEE predicts a change in FM  in younger adults , who as a group gained weight in this study . In contrast , baseline PAEE  in older adults -- who were on average weight stable -- is associated with a gain in BW , which was explained by an increase in FM and FFM PURPOSE Findings from prospect i ve studies on associations between physical activity and adiposity among youth are inconsistent . Our aim was to describe physical activity trajectories during secondary school and examine the association with change in adiposity in youth . METHODS  Physical activity  was measured in 20 survey cycles from 1999 to 2005 ; anthropometrics were measured in survey cycles 1 , 12 , and 19 . Individual growth curves modeling moderate-to-vigorous physical activity ( MVPA ) and vigorous physical activity ( VPA ) were estimated . Estimates of initial level and rate of decline in MVPA and VPA bouts per week were included as potential predictors of body fat% and body mass index using age- and sex-specific linear regression . RESULTS Complete data were available for 840 and 760 adolescents aged 12 - 13 years at baseline , followed from survey cycles 1 - 12 and 12 - 19 , respectively . Among girls , yearly declines of one MVPA and one VPA bout per week during earlier adolescence were associated with increases of 0.19 ( 95 % confidence interval [ CI ] , 0.02 - 0.36 ) and 0.47 ( 95 % CI , 0.015 - 0.92 ) units of body fat% , respectively . In boys , a yearly decline of one MVPA bout per week was associated with an increase of 0.38 ( 95 % CI , 0.05 - 0.70 ) units of body fat% during later adolescence . CONCLUSIONS Obes 
    Output:
    
agent
Question naires were the more predominant way to evaluate PA .
Most studies showed that PA promotes a protective effect against a higher BF gain .
CONCLUSION It was concluded that PA has a protective effect against BF with differences between the genders and according to the BF marker or measurement assessed ; higher intensity PA leads to a greater effect against BF gain in both genders ; and the maintenance or increase of PA level on BF observed through analysis of change in PA level yielded more consistent findings in the relation between PA and BF
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Overweight and obesity affects more than 66 % of the adult population and is associated with a variety of chronic diseases . Weight reduction reduces health risks associated with chronic diseases and is therefore encouraged by major health agencies . Guidelines of the National Heart , Lung , and Blood Institute ( NHLBI ) encourage a 10 % reduction in weight , although considerable literature indicates reduction in health risk with 3 % to 5 % reduction in weight . Physical activity ( PA ) is recommended as a component of weight management for prevention of weight gain , for weight loss , and for prevention of weight regain after weight loss . In 2001 , the American College of Sports Medicine ( ACSM ) published a Position St and that recommended a minimum of 150 min wk(-1 ) of moderate-intensity PA for overweight and obese adults to improve health ; however , 200 - 300 min wk(-1 ) was recommended for long-term weight loss . More recent evidence has supported this recommendation and has indicated more PA may be necessary to prevent weight regain after weight loss . To this end , we have reexamined the evidence from 1999 to determine whether there is a level at which PA is effective for prevention of weight gain , for weight loss , and prevention of weight regain . Evidence supports moderate-intensity PA between 150 and 250 min wk(-1 ) to be effective to prevent weight gain .  Moderate-intensity PA between 150 and 250 min wk(-1 ) will provide only modest weight loss . Greater amounts of PA ( > 250 min wk(-1 ) ) have been associated with clinical ly significant weight loss .  Moderate-intensity PA between 150 and 250 min wk(-1 ) will improve weight loss in studies that use moderate diet restriction but not severe diet restriction . Cross-sectional and prospect i ve studies indicate that after weight loss , weight maintenance is improved with PA > 250 min wk(-1 ) . However , no evidence from well- design ed r and omized controlled trials exists to judge the effectiveness of PA for prevention of weight regain after weight loss .  Resistance training does not enhance weight loss but may increase fat-free mass and increase loss of fat mass and is associated with reductions in health risk . Existing evidence indicates that endurance PA or resistance training without weight loss improves health risk . There is inadequate evidence to determine whether PA prevents or attenuates detrimental changes in chronic disease risk during weight gain BACKGROUND The proportion of overweight adolescents has increased , but the behavioral risk factors for overweight youth are not well understood . OBJECTIVE To examine how diet , physical activity , and sedentary behaviors relate to overweight status in adolescents . DESIGN AND SETTING Baseline data from the Patient-Centered Assessment and Counseling for Exercise Plus Nutrition Project , a r and omized controlled trial of adolescents to determine the effects of a clinic-based intervention on physical activity and dietary behaviors . PARTICIPANTS A total of 878 adolescents aged 11 to 15 years , 42 % of whom were from minority background s. MAIN OUTCOME MEASURE Centers for Disease Control and Prevention body mass index-for-age percentiles divided into 2 categories : normal weight ( < 85th percentile ) and at risk for overweight plus overweight ( AR + O ) ( > or=85th percentile ) . RESULTS Overall , 45.7 % of the sample was classified as AR + O with a body mass index for age at the 85th percentile or higher . More girls from minority background s ( 54.8 % ) were AR + O compared with non-Hispanic white girls ( 42 % ) ( chi(2)(1 ) = 7.6 ; P = .006 ) . Bivariate analyses indicated that girls and boys in the AR + O group did fewer minutes per day of vigorous physical activity , consumed fewer total kilojoules per day , and had fewer total grams of fiber per day than those in the normal-weight group . Boys in the AR + O group also did fewer minutes per day of moderate physical activity and watched more minutes per day of television on nonschool days than normal-weight boys . Final multivariate models indicated that independent of socioeconomic status ( as assessed by household education level ) , girls had a greater risk of being AR + O if they were Hispanic or from another minority background ( odds ratio [ OR ] = 1.65 ; 95 % confidence interval [ CI ] , 1.09 - 2.49 ) and a reduced risk of being AR + O as minutes per day of vigorous physical activity increased ( OR = 0.93 ; 95 % CI , 0.89 - 0.97 ) . A low level of vigorous physical activity was the only significant risk factor for boys being AR + O ( OR = 0.92 ; 95 % CI , 0.89 - 0.95 ) . Analyses based on meeting behavioral guidelines supported these findings and showed that failing to meet the 60 min/d moderate to vigorous physical activity guideline was associated with overweight status for both girls and boys . In addition , boys who failed to meet sedentary behavior and dietary fiber guidelines were more likely to be overweight . CONCLUSIONS Of the 7 dietary and physical activity variables examined in this cross-sectional study , insufficient vigorous physical activity was the only risk factor for higher body mass index for adolescent boys and girls . Prospect i ve studies are needed to clarify the relative importance of dietary and physical activity behaviors on overweight in adolescence BACKGROUND It is unclear how moderate and vigorous intensities of physical activity ( PA ) are associated with cardiovascular fitness ( CVF ) and percentage of body fat ( % BF ) in adolescents . OBJECTIVE We tested the hypothesis that vigorous PA , to a greater degree than moderate PA , would be associated with better CVF and lower % BF . DESIGN This was a cross-sectional study of 421 black and white high school students ( x age : 16 y ) .  PA was measured with 5 d of accelerometry and expressed in min/d of moderate or vigorous PA .  CVF was measured with a multistage treadmill test and was expressed as the oxygen consumption at a heart rate of 170 bpm . % BF was measured with dual-energy X-ray absorptiometry . Multiple regressions were used to determine the degree to which variance in CVF and % BF was explained by PA , after control for age , sex , race , and the sex x race interaction . RESULTS A higher index for CVF was associated with higher amounts of moderate and vigorous PA ;  more variance was explained by vigorous than by moderate PA .  Lower % BF was associated with higher amounts of vigorous PA but not with the amount of moderate PA . CONCLUSION Black and white adolescents who engaged in relatively large amounts of free-living vigorous exercise were likely to be relatively fit and lean BACKGROUND Little is known about how the intensity of exercise influences cardiovascular fitness and body composition , especially in obese adolescents . OBJECTIVE Our goal was to determine the effects of physical training intensity on the cardiovascular fitness , percentage of body fat ( % BF ) , and visceral adipose tissue ( VAT ) of obese adolescents . DESIGN Obese 13 - 16-y-olds ( n = 80 ) were assigned to 1 ) biweekly lifestyle education ( LSE ) , 2 ) LSE + moderate-intensity physical training , or 3 ) LSE + high-intensity physical training . The intervention lasted 8 mo . Physical training was offered 5 d/wk , and the target energy expenditure for all subjects in physical training groups was 1047 kJ ( 250 kcal)/session . Cardiovascular fitness was measured with a multistage treadmill test , % BF with dual-energy X-ray absorptiometry , and VAT with magnetic resonance imaging . RESULTS The increase in cardiovascular fitness in the high-intensity physical training group , but not in the moderate-intensity group , was significantly greater than that in the LSE alone group ( P = 0.009 ) ; no other comparisons of the 3 groups were significant . Compared with the LSE alone group , a group composed of subjects in both physical training groups combined who attended training sessions > or=2 d/wk showed favorable changes in cardiovascular fitness ( P < 0.001 ) , % BF ( P = 0.001 ) , and VAT ( P = 0.029 ) . We found no evidence that the high-intensity physical training was more effective than the moderate-intensity physical training in enhancing body composition . CONCLUSIONS The cardiovascular fitness of obese adolescents was significantly improved by physical training , especially high-intensity physical training . The physical training also reduced both visceral and total-body adiposity , but there was no clear effect of the intensity of physical training BACKGROUND Body mass index ( BMI ) during adolescence is predictive of BMI at adult age . However , BMI can not distinguish between lean and fat body mass . Skinfold thickness may be a better predictor of body fatness . OBJECTIVE The objective of this study was to evaluate the relations between BMI and skinfold thickness during adolescence and body fatness during adulthood . DESIGN We included 168 men and 182 women from the Amsterdam Growth and Health Longitudinal Study , a prospect i ve study that conducted 8 measurements of BMI and skinfold thickness between 1976 and 2000 .  BMI and skinfold thickness during adolescence were analyzed in relation to adult body fatness measured at a mean age of 37 y with dual-energy X-ray absorptiometry . RESULTS None of the boys and 1.7 % of the girls were overweight at baseline , whereas the prevalence of high body fatness during adulthood was 29 % in men and 32 % in women . At the ages of 12 - 16 y , skinfold thickness was more strongly associated with adult body fatness than was BMI . Age-specific relative risks for a high level of adult body fatness varied between 2.3 and 4.0 in boys and between 2.1 and 4.3 in girls in the highest versus the lowest tertile of the sum of 4 skinfold thicknesses . For the highest tertile of BMI , the relative risk varied between 0.8 and 2.1 in boys and between 1.3 and 1.8 in girls . CONCLUSION Skinfold thickness during adolescence is a better predictor of high body fatness during adulthood than is BMI during adolescence BACKGROUND It is unclear whether physical activity energy expenditure ( PAEE ) predicts changes in body composition . OBJECTIVE The objective was to describe the independent associations between PAEE and changes in body composition in a population -based cohort . DESIGN This was a prospect i ve population -based study conducted in 739 ( 311 men and 428 women ) healthy middle-aged ( median age : 53.8 y ) whites . The median follow-up was 5.6 y. PAEE ( MJ/d ) was assessed by heart rate monitoring , individually calibrated by using the FLEX heart rate method .  Fat mass ( FM ) and fat-free mass ( FFM ) were assessed by bioimpedance . RESULTS Body weight ( BW ) at follow-up was significantly related to baseline PAEE ( P < 0.05 ) after adjustment for sex , baseline age , FM , FFM , and follow-up time . A significant interaction between PAEE and age ( P = 0.023 ) was observed . After the subjects were stratified ( above and below the median for age ) , BW increased by a mean ( + /-SD ) of 1.7 + /- 5.9 kg ( P < 0.0001 ) in the younger cohort . In this group , follow-up FM was significantly associated with baseline PAEE ( P = 0.036 ) after adjustment for confounders . In the older cohort , BW did not change between baseline and follow-up . In this group , in contrast with the younger population , follow-up BW , FM , and FFM were all significantly and positively associated with baseline PAEE ( P < 0.01 for all ) . CONCLUSIONS Baseline PAEE predicts a change in FM  in younger adults , who as a group gained weight in this study . In contrast , baseline PAEE  in older adults -- who were on average weight stable -- is associated with a gain in BW , which was explained by an increase in FM and FFM PURPOSE Findings from prospect i ve studies on associations between physical activity and adiposity among youth are inconsistent . Our aim was to describe physical activity trajectories during secondary school and examine the association with change in adiposity in youth . METHODS  Physical activity  was measured in 20 survey cycles from 1999 to 2005 ; anthropometrics were measured in survey cycles 1 , 12 , and 19 . Individual growth curves modeling moderate-to-vigorous physical activity ( MVPA ) and vigorous physical activity ( VPA ) were estimated . Estimates of initial level and rate of decline in MVPA and VPA bouts per week were included as potential predictors of body fat% and body mass index using age- and sex-specific linear regression . RESULTS Complete data were available for 840 and 760 adolescents aged 12 - 13 years at baseline , followed from survey cycles 1 - 12 and 12 - 19 , respectively . Among girls , yearly declines of one MVPA and one VPA bout per week during earlier adolescence were associated with increases of 0.19 ( 95 % confidence interval [ CI ] , 0.02 - 0.36 ) and 0.47 ( 95 % CI , 0.015 - 0.92 ) units of body fat% , respectively . In boys , a yearly decline of one MVPA bout per week was associated with an increase of 0.38 ( 95 % CI , 0.05 - 0.70 ) units of body fat% during later adolescence . CONCLUSIONS Obes 
    Output:
    