title: American College of Sports Medicine Position Stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Diet, physical activity, and sedentary behaviors as risk factors for overweight in adolescence. Relations of moderate and vigorous physical activity to fitness and fatness in adolescents. Effects of exercise intensity on cardiovascular fitness, total body composition, and visceral adiposity of obese adolescents. Adolescent skinfold thickness is a better predictor of high body fatness in adults than is body mass index: the Amsterdam Growth and Health Longitudinal Study. Physical activity energy expenditure predicts changes in body composition in middle-aged healthy whites: effect modification by age. Physical activity growth curves relate to adiposity in adolescents. Active Commuting Throughout Adolescence and Central Fatness before Adulthood: Prospective Birth Cohort Study Bidirectional cross-sectional and prospective associations between physical activity and body composition in adolescence: Birth cohort study Prospective associations between objective measures of physical activity and fat mass in 12-14 year old children: the Avon Longitudinal Study of Parents and Children (ALSPAC) ENERGY BALANCE IN ADOLESCENT GIRLS: THE TRIAL OF ACTIVITY FOR ADOLESCENT GIRLS COHORT Relation between the changes in physical activity and body-mass index during adolescence: a multicentre longitudinal study A prospective examination of children's time spent outdoors, objectively measured physical activity and overweight Associations of body size and composition with physical activity in adolescent girls. Effect of long-term leisure time physical activity on lean mass and fat mass in girls during adolescence. Physical activity and healthy weight maintenance from childhood to adulthood. BMI-related errors in the measurement of obesity Relationships of activity and sugar drink intake on fat mass development in youths. Adiposity, lipid levels, and brief endurance training in nonobese adolescent males.
abstract: 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 Obesity prevention programs should include strategies to prevent declines in physical activity Background Active commuting is a good opportunity to accumulate physical activity ( PA ) across the lifespan that potentially might influence central body fat . We aim ed to examine the prospect i ve associations of active commuting at 11 , 15 and 18 years of age with central body fat at 18 years . Methods Participants were part of a large birth cohort study in Pelotas , Brazil ( n = 3,649 participants ) .  Active commuting , leisure-time PA and income  were self-reported at 11 , 15 and 18 years . Waist circumference and trunk fat mass were collected at 18 years with the use of a 3-dimensional photonic scanner and dual-energy X-ray absorptiometry , respectively . Results Active commuting at 11 years was not prospect ively associated with central body fat . However , we found that active commuting at 15 and 18 years were prospect ively and cross-sectionally associated with central body fat variables , respectively , in boys but not in girls . Also , boys in the highest tertile of accumulated active commuting ( i.e. , average of active commuting at 11 , 13 and 18 years ) were associated with −2.09 cm ( 95%CI : −3.24 ; −0.94 ) of waist circumference and −1.11 kg ( 95%CI : −1.74 ; −0.48 ) of trunk fat mass compared to boys in the lowest tertile . Analyses on changes in tertiles of active commuting from 11 and 15 years to 18 years with central body fat variables at 18 years showed that boys who remained consistently in the highest tertile or moved to a higher tertile had lower levels of central body fat compared to those consistently in the lowest tertile . Conclusions Active commuting throughout adolescence in boys , especially during middle and late adolescence , is associated with lower levels in central fatness before adulthood Abstract The aim of this study was to investigate the cross-sectional and prospect i ve associations between physical activity and  body composition in adolescence . This is a prospect i ve study , including 4,103 adolescents belonging to the Pelotas ( Brazil ) 1993 birth cohort , who were followed up at the mean ages of 11.3 and 14.7 years . Sub sample analyses included 511 individuals with accelerometry and deuterium dilution data at 13.3 years .  Sum of skinfolds at age 11.3 years was highly correlated with skinfolds at age 14.7 years ( rho = 0.74 , P < 0.001 ) . More than 85 % of participants remained in the same quintile or changed by not more than one quintile during the 3.4 year period .  Tracking of physical activity  was considerably lower , although still significant ; the correlation was 0.24 ( P < 0.001 ) and 61.4 % of the adolescents moved one or less quintiles . In fully-adjusted models , no significant cross-sectional or longitudinal associations were found between physical activity and body composition , neither in boys nor in girls . These null results were confirmed in the 511 individuals with accelerometry and deuterium data . We provide evidence of  tracking of physical activity and particularly body composition during adolescence . Our results do not support the hypothesis that physical activity and fatness are strongly related in adolescents Objective To investigate associations between physical activity at age 12 and subsequent adiposity at age 14 . Design Prospect i ve birth cohort study with data collected between 2003 and 2007 . Setting Original recruitment in 1991 - 2 of 14 541 pregnant women living in the former County of Avon ( United Kingdom ) . Participants At age 12 , 11 952 children were invited to attend the research clinic . Of these , 7159 attended , and 4150 ( 1964 boys , 2186 girls ) provided sufficient data on exposure , outcome , and confounding variables . Main outcome measure Fat mass at age 14 , measured by dual emission x ray absorptiometry , associated with physical activity at age 12 , measured by accelerometry . Results Prospect i ve associations of fat mass at age 14 ( outcome ) with physical activity at age 12 ( exposure ) were strong for both  total activity ( accelerometer counts/min ) and for daily amount of moderate-vigorous physical activity  ( min/day ) . An extra 15 minutes of moderate-vigorous physical activity per day at age 12 was associated with lower fat mass at age 14 in boys ( by 11.9 % ( 95 % confidence interval 9.5 % to 14.3 % ) ) and girls ( by 9.8 % ( 6.7 % to 12.8 % ) ) . The proportion of physical activity due to moderate-vigorous physical activity was between 20 % and 30 % in boys and girls at the two ages . Conclusions Higher levels of physical activity , in particular activity of moderate to higher intensities , are prospect ively associated with lower levels of fat mass in early adolescence . Interventions to raise levels of physical activity in children are likely to be important in the fight against obesity Objectives To study correlates of change in BMI percentile and body fat among adolescent girls Design and Methods A longitudinal prospect i ve study following 265 girls from the Trial of Activity for Adolescent Girls ( TAAG ) cohort measured in 8th grade and during 10 and 11th grade or 11th and 12th grade . Twice during 2009 - 2011 girls wore an accelerometer and completed a food frequency question naire and 7-day diary documenting trips and food eaten away from home and school . Physical activity , BMI , and percent body fat were objective ly measured at each time point . Results Moderate to vigorous physical activity ( MVPA ) declined , but was not independently associated with changes in BMI percentile . Increased vigorous physical activity was associated with reductions in body fat . Diet was associated with both changes in BMI percentile and body fat . Girls who increased the percentage of caloric intake from snacks and desserts reduced their BMI percentile and body fat . Conclusions Some relationships between energy balance behaviors and BMI and body composition were counter-intuitive . While it is plausible that vigorous activity would result in reductions of body fat , until more accurate methods are devised to measure diet , the precise contribution of dietary composition to health will be difficult to assess BACKGROUND The role of physical activity in preventing obesity during adolescence remains unknown . We examined changes in activity in relation to changes in body-mass index ( BMI ) and adiposity in a cohort of 1152 black and 1135 white girls from the USA , who were followed up prospect ively from ages 9 or 10 to 18 or 19 years . METHODS BMI and sum of skinfold thickness were assessed annually , whereas habitual activity was assessed at years 1 ( baseline ) , 3 , 5 , and 7 - 10 . Each girls ' overall activity status was categorised as active , moderately active , or inactive . Longitudinal regression models examined associations between changes in activity and in overall activity status with changes in BMI and in sum of skinfold thickness . FINDINGS Each decline in activity of 10 metabolic equivalent [MET]-times per week was associated with an increase in BMI of 0.14 kg/m2 ( SE 0.03 ) and in sum of skinfold thickness of 0.62 mm ( 0.17 ) for black girls , and of 0.09 kg/m2 ( 0.02 ) and 0.63 mm ( 0.13 ) for white girls . At ages 18 or 19 years , BMI differences between active and inactive girls were 2.98 kg/m2 ( p<0.0001 ) for black girls and 2.10 kg/m2 ( p<0.0001 ) for white girls . Similar results were apparent for sum of skinfold thickness . For moderately active girls , changes in BMI and sum of skinfold thickness were about midway between those for active and inactive girls . INTERPRETATION Changes in activity levels of US girls during adolescence significantly affected changes in BMI and adiposity . Thus , preventing the steep decline in activity during adolescence is an important method to reduce obesity Objective : This study aim ed to determine whether time spent outdoors was associated with objective ly measured physical activity , body mass index ( BMI ) z-score and overweight in elementary-school aged children , cross-sectionally and prospect ively over 3 years . Methods : Three-year cohort study with data collected during 2001 and 2004 . Nineteen r and omly selected state elementary schools across Melbourne , Australia . One hundred and eighty eight 5–6-year-old and 360 10–12-year-old children . Baseline parent reports of children 's time spent outdoors  during warmer and cooler months , on weekdays and weekends . At baseline and follow-up , children 's moderate and vigorous physical activity ( MVPA ) was objective ly assessed by accelerometry , and BMI z-score and overweight was calculated from measured height and weight . Results : Cross-sectionally , each additional hour outdoors on weekdays and weekend days during the cooler months was associated with an extra 27 min week−1 MVPA among older girls , and with an extra 20 min week−1 MVPA among older boys . Longitudinally , more time outdoors on weekends predicted higher MVPA on weekends among older girls and boys ( 5 min week−1 ) . The prevalence of overweight among older children at follow-up was 27–41 % lower among those spending more time outdoors at baseline . Conclusion : Encouraging 10–12-year-old children to spend more time outdoors may be an effective strategy for increasing physical activity and preventing increases in overweight and obesity . Intervention research investigating the effect of increasing time outdoors on children 's physical activity and overweight is warranted PURPOSE To examine whether components of body composition ( size , fat mass , and fat-free mass ) were related to physical activity . METHODS A r and om sample of 60 eligible sixth grade girls at each of 36 schools ( six schools per region and six regions in total sample ) ; complete measurements on 1,553 girls .  Physical activity was assessed over 6 d in each girl using an accelerometer , and body composition was assessed using a multiple regression equation using body mass index and triceps skinfold . Minutes of moderate-to-vigorous and vigorous physical activity  were estimated from accelerometer counts per 30 s above threshold values determined from a previous study . RESULTS Significant inverse relationships were found for all measures of body size and composition and all physical activity indices . The combination of fat and fat-free mass expressed as a weight and as an index ( divided by height squared ) along with race , SES , site , and school were most highly associated with physical activity in multiple regression analysis , accounting for 14 - 15 % of the variance in physical activity . Fat mass was more closely related to moderate-to-vigorous physical activity ( MVPA ) and vigorous physical activity ( VPA ) than fat-free mass with higher st and ardized regression coefficients . CONCLUSION We conclude that both fat mass or fat mass index as well as fat-free mass or fat-free mass index make independent contributions in association with physical activity levels . These indices are recommended for future studies The purpose of this 7-yr prospect i ve longitudinal study was to examine if the level and consistency of leisure-time physical activity ( LTPA ) during adolescence affected the quantity and distribution of lean mass ( LM ) and fat mass ( FM ) at early adulthood . The study subjects were 202 Finnish girls who were 10 - 13 yr old at baseline .  LM and FM of the total body ( TB ) , arms , legs , and trunk were assessed by dual-energy X-ray absorptiometry . Muscle cross-sectional area ( mCSA ) of the left leg was assessed by peripheral quantitative computed tomography . Scores of LTPA were obtained by question naire . Girls were divided into four groups comprising those with consistently low ( G(LL ) ) or consistently high ( G(HH ) ) physical activity , or those whose physical activity changed from low to high ( G(LH ) ) , or from high to low ( G(HL ) ) , over the 7 yr of follow-up . At baseline , no differences were found in LM , FM , and FM% among the groups in any of the body segments . By the end of the study G(HH ) and G(LH ) had higher values of LM of the TB , arms , legs , and trunk than that of the G(HL ) and G(LL ) groups ( P < 0.05 , respectively ) . High FM% of the TB was associated with low level of LTPA , but no significant differences were found in the absolute amount of FM and mCSA among the LTPA groups . Our results suggest that a consistently high level of  LTPA  during the transition from prepuberty to early adulthood has a positive effect on lean mass gain in girls . Participating in 5 h of LTPA per week had a significant effect on FM% but not on the absolute amount of fat mass The objective of this study was to determine whether change in physical activity was associated with maintaining a healthy weight from childhood to adulthood . This prospect i ve cohort study examined 1,594 young Australian adults ( 48.9 % female ) aged 27 - 36 years who were first examined at age 9 - 15 years as part of a national health and fitness survey .  BMI was calculated from measured height and weight , and physical activity was self-reported at both time points ; pedometers were also used at follow-up . Change in  physical activity  was characterized by calculating the difference between baseline and follow-up z-scores . Change scores were categorized as decreasing ( large , moderate ) , stable , or increasing ( large , moderate ) . Healthy weight was defined in childhood as a BMI less than international overweight cutoff points , and in adulthood as BMI < 25 kg/m(2 ) . Healthy weight maintainers were healthy weight at both time points . Compared with those who demonstrated large relative decreases in physical activity , females in all other groups were 25 - 37 % more likely to be healthy weight maintainers , although associations differed according to the physical activity measure used at follow-up and few reached statistical significance . Although younger males whose relative physical activity moderately or largely increased were 27 - 34 % more likely to be healthy weight maintainers than those whose relative physical activity largely decreased , differences were not statistically significant . In conclusion , relatively increasing and stable physical activity from childhood to adulthood was only weakly associated with healthy weight maintenance . Examining personal , social , and environmental factors associated with healthy weight maintenance will be an important next step in underst and ing why some groups avoid becoming overweight Body mass index ( BMI ) has various deficiencies as a measure of obesity , especially when the BMI measure is based on self-reported height and weight . BMI is an indirect measure of body fat compared with more direct approaches such as bioelectrical impedance . Moreover , BMI does not necessarily reflect the changes that occur with age . The proportion of body fat increases with age , whereas muscle mass decreases , but corresponding changes in height , weight and BMI may not reflect changes in body fat and muscle mass . Both the sensitivity and specificity of BMI have been shown to be poor . Additionally , the relation between BMI and percentage of body fat is not linear and differs for men and women . The consequences of the errors in the measurement of obesity with BMI depend on whether they are differential or nondifferential . Differential misclassification , a potentially greater problem in case – control and cross-sectional studies than in prospect i ve cohort studies , can produce a bias toward or away from the null . Nondifferential misclassification produces a bias toward the null for a dichotomous exposure ; for measures of exposure that are not dichotomous , the bias may be away from the null . In short , the use of BMI as a measure of obesity can introduce misclassification problems that may result in important bias in estimating the effects related to obesity PURPOSE To determine whether a significant relationship exists between fat mass ( FM ) development and physical activity ( PA ) and /or sugar-sweetened drink ( SD ) consumption in healthy boys and girls aged 8 - 19 yr . METHODS A total of 105 males and 103 females were assessed during childhood and adolescence for a maximum of 7 yr and a median of 5 yr . Height was measured biannually . Fat-free mass ( FFM ) and FM were assessed annually by dual x-ray absorptiometry ( DXA ) . PA  was evaluated two to three times annually using the PAQ-C/A. Energy intake and SD were assessed using a 24-h dietary intake question naire also completed two to three times per year . Years from peak height velocity were used as a biological maturity age indicator . Multilevel r and om effects models were used to test the relationship . RESULTS When controlling for maturation , FFM , and energy intake adjusted for SD ,  PA level was negatively related to FM development in males ( P<0.05 ) but not in females ( P>0.05 ) . In contrast , there was no relationship between SD and FM development of males or females ( P>0.05 ) . There was also no interaction effect between SD and PA  ( P>0.05 ) with FM development . CONCLUSION This finding lends support to the idea that increasing PA in male youths aids in the control of FM development . Models employed showed no relationship between SD and FM in either gender Physical activity during childhood and adolescence may influence the development of childhood obesity and cardiovascular disease later in life . Research focused prospect ively on the effects of training on lipid levels in nonobese subjects , and studies using noninvasive measurements of subcutaneous and intraabdominal fat are lacking . It was hypothesized in nonobese sedentary adolescent males that a brief endurance-type exercise training intervention would reduce body fat and improve lipid profiles .  Thirty-eight healthy , nonobese sedentary adolescent males ( mean age 16 + /- 0.7 years old ; 18 controls , 20 trained ) completed a 5-week prospect i ve , r and omized , controlled study . Adiposity was measured using magnetic resonance images of the thigh and abdomen ( subcutaneous abdominal adipose tissue [ SAAT ] and intraabdominal adipose tissue [ IAAT ] ) . Lipid measurements included serum triglycerides ( TG ) , total cholesterol ( TC ) , HDL and LDL cholesterol . There was no change in body weight in either control or training groups . Training led to small but significant reductions in thigh fat ( -4.6 + /- 1.5 % , p < 0.03 ) and SAAT% ( 1.7 + /- 0.8 % , p < 0.02 ) . There was no change in IAAT% . Unexpectedly in the control group there were significant increases in thigh fat ( 5.2 + /- 1.7 % , p<0.01 ) , SAAT% ( 1.8 + /- 0.6 , p < 0.007 ) and IAAT% ( 4.5 + /- 1.1 , p < 0.0007 ) . Training-induced changes in adiposity were not accompanied by changes in circulating lipids . In nonobese adolescent males a brief period of endurance training led to reductions in body fat depots without weight change while body fat increased rapidly in the control group . Exercise training did not change lipid levels , the latter may require more sustained alterations in patterns of physical activity
target: 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
background: BACKGROUND Physical activity ( PA ) practice has been inversely associated to body  fat ( BF ) and recommended as a way to reduce and prevent obesity .
  The objective of this study was to conduct a systematic review on the association of  PA and BF in adolescence .