in most industrialized countries , including germany , the prevalence of overweight and obesity in children and adolescents has increased over the last decades [ 13 ] .
this has also led to the occurrence of various metabolic or cardiovascular disease risks , previously only observed in adults [ 4 , 5 ] .
in addition to higher risks for cardiovascular disease and type ii diabetes , increased body weight has been associated with psychosocial problems such as depression or low self - esteem   and decreased overall quality of life .
as excessive body weight tracks into adulthood and increases the risk for cvd , diabetes , or cancer [ 8 , 9 ] , childhood overweight has also been associated with premature mortality [ 1012 ] .
overweight or obesity is a complex phenotype but various risk factors such as low levels of physical activity ( pa ) and increased sedentary behavior , parental obesity and activity levels [ 14 , 15 ] , or socioeconomic status   have been identified .  
along with the change in body composition a secular decline in physical fitness and motor ability in children has been observed [ 1719 ] .
the decline was most pronounced for aerobic fitness , which is associated with reduced cvd risk [ 21 , 22 ] .
a commonly discussed reason for the decline in physical fitness is low levels of moderate - to - vigorous physical activity [ 23 , 24 ] .
specifically a decline in habitual physical activity including active transport has been observed [ 25 , 26 ] . on the other hand participation in organized sports
in germany , 70.2% of 7- to 10-year - old children are involved in sports clubs .
this number also reflects the importance of sports clubs concerning social integration and development of the personality [ 30 , 31 ] in addition to physical fitness and health . due to its popularity
, sports participation should be considered as an effective strategy to reduce fatness and increase fitness in children [ 3234 ] .
the world health organisation ( who ) also promotes the use of existing settings based on the national situation and cultural habits for the prevention of overweight and obesity .  
while an inverse relationship between body composition and extracurricular sports participation was shown in adolescents , no such relationship was shown in primary school children .
quinto romani   concludes that the literature examining the effects of organized sports on children 's weight status or physical fitness is inconclusive .
in addition to problems of accurate assessment , sports participation in organized youth sports does not necessarily guarantee sufficient physical activity to achieve health benefits or increase fitness .
further , various environmental factors need to be considered when examining the effect of sports participation on body composition and fitness .
the purpose of the study , therefore , was to examine the association between participation in organized sports and physical fitness as well as overweight in 8-year - old children while considering various environmental constraints .
baseline data from 1119 ( 53% male , 47% female ) second - grade children ( 7.6  0.4 years ) from 32 schools ( 64 classes ) participating in a health and lifestyle intervention project ( urmel - ice ) in southwest germany was used .
the study protocol was approved by the institutional ethics review board , and parental consent as well as child assent was obtained prior to data collection .
height and weight were measured in 1064 children ( 95% of the total sample ) according to standard procedures during a physical examination performed by the outpatient clinic of the children 's hospital .
height was measured to the nearest 0.1  cm ( ulm stadiometer , busse , ulm , germany ) and weight to the nearest 0.1  kg using a calibrated balance beam scale ( seca , hamburg , germany ) with participants wearing only underwear .
body mass index ( bmi ) was calculated ( kg / m ) and converted to bmi percentiles ( bmipct ) using kromeyer - hauschild et al .  
( general motor abilities test for children ) , a commonly used fitness test for 6- to 11-year - old children , was administered in the schools by trained personnel .
in addition to the 6 items of the ast ( 6  min run , 20  m sprint , medicine ball throw , throw - on - target , throw - and - turn , and obstacle run ) sit - and - reach test and one - leg - balancing from the eurofit test   were incorporated to cover a wider range of fitness - related parameters .
a total of 995 children ( 89% of all participating children ) participated in these physical fitness tests .  
a parental questionnaire was used to determine participation in organized sports outside the school setting .
as there is currently no validated instrument for the assessment of health behaviour available in german , questions were based on the kiggs survey , which assessed health behaviour in 18,000 german children and adolescents .
children 's sports participation was classified as less than once a week , once or twice a week , and more than twice a week .   
in addition , the questionnaire assessed confounding variables such as migration background , parental education , parental overweight and parental participation in organized sports . confounding variables were dichotomized .
migration background was present when either the child 's father or mother was born outside germany or when a foreign language was spoken during the child 's first years .
level of parents ' education was differentiated by 10 years of schooling of either father or mother .
a bmi cutpoint of 25 was used to determine between overweight and nonoverweight , and parental sports participation was separated by participation in organized sports or visiting a fitness centre more than one hour per week .  
descriptive statistics for the three sports participation groups were calculated and checked for normal distribution .
the odds ratio for children being overweight as well as sports participation was calculated via multiple stepwise logistic regression entering sex , overweight , migration background , level of parents ' education , parental overweight , and parental participation in sports as confounding variables .
in addition , the child 's weight status was considered for the sports participation model , while sports participation was considered when calculating the odds ratio for being overweight .
differences in individual fitness parameters by sports participation were calculated via multivariate analysis of covariance ( mancova ) , again adjusting for the previously mentioned confounding variables .
missing values were excluded per case , and level of significance was defined as p < 0.05 .

 table 1 shows age and anthropometric data of the total sample by sports participation .
the majority of children ( 60% ) participated in sports once or twice per week beyond the recommended 3 classes of pe .
bmipct differed significantly between sports participation groups ( f ( 2 , 1004 ) = 6.81 , p < 0.01 ) . specifically , those reporting sports participation 1 - 2 times per week had significantly lower bmipct than those reporting less than once a week .  

table 2 displays the prevalence of potential confounding variables on child 's sports participation . after entering all of these variables as well as sex in a multiple stepwise logistic regression , comparing children who participate less than once with those participating regularly in organized sports , only migration background as well as parental weight status remained in the final model , which explained between 11.2% ( cox and snell r ) and 16.4% ( nagelkerke r ) of the variance in sports participation . having a migration background or overweight parents reduced the odds for regular sports participation .
it was further shown that the odds of children being overweight were significantly lower with increased sports participation ( table 3 ) .  
using mancova , controlling for sex , overweight , migration background , parental overweight , and parental participation in organized sport , a significant main effect of participation in organized sports on most physical fitness parameters was shown ( table 4 ) .
post hoc analysis using bonferroni adjustment revealed that children who participate less than once a week in organized sports performed significantly worse than those who participate regularly .
there were no differences between children participating once or twice per week in organized sports compared to those participating more often .
no significant differences occurred for the 20  m sprint and obstacle run , even though there was a tendency of a better performance with higher sports participation .
  in the present study 12.4% of children were overweight or obese , which is comparable to previously reported percentages in germany and other european countries [ 4345 ] .
similarly , participation rates in organized sports are comparable to those reported previously in german children . the inverse relationship between fitness and overweight as well as physical activity and overweight has generally been accepted .
this study , however , further shows that this association remains even after controlling for various family - related confounding variables .
these results suggest that sports participation is an important aspect when examining overweight and physical fitness , even at a relatively young age .
regular participation in organized sports , even only once or twice per week , already reduced the odds for being overweight by almost 50% .
similar results have been reported in adolescents [ 37 , 47 ] , 10- to 11-year - old children , and in preschoolers .
interestingly , no association between sports participation and body fatness was observed in studies examining similar age groups [ 36 , 49 ] .
one explanation for these results may be that bmi does not necessarily differentiate between body fat and lean tissue .
a lower amount of body fat in children with higher sports participation could be masked by a higher lean body mass , which would result in no differences in bmi .
, however , relied on skinfold measurements rather than bmi but could not show any association between bmi and sports participation either .
further , only limited information on the type of sports children are engaging in is available , and different sports may affect body composition differently .
in addition , sports participation is only one component of children 's physical activity , and especially younger children probably obtain the majority of their physical activity via free play , which may also differ significantly in intensity .
nevertheless , engagement in organized sports has been associated with long - term engagement in physical activity .
the present study also indicates that migration status as well as parental weight status needs to be considered when examining the association between sports participation and body weight in children .
parental overweight as well as lower socio - economic status has been shown to be associated with a higher body weight in children .
migration status is also commonly associated with lower socioeconomic status   but a recent study in a german sample showed an inverse relationship between migration status and sports participation independent of household income or parental education .
this could be due to different cultural values and attitudes towards sports . even though migration status is associated with educational level , no significant association between parental education and overweight in children
van der horst et al .   also argued that parental support , such as transportation to training and competition , is a crucial component concerning children 's sports participation .
this kind of support seems to be more important than parents serving as role models , but more active parents are probably more likely to provide transportation or other forms of support for their children . in addition , a significant relationship between sports participation and various components of physical fitness has been shown , independent of migration background , parental education , and parental sports participation .
particularly the role of regular sports participation in aerobic fitness should be emphasized as the inverse association between aerobic fitness and cardiovascular disease risk has already been reported in children .
regular sports participation also increases power , flexibility , and balance [ 36 , 57 ] .
the better performance in these components may be crucial for continued engagement in sports and physical activity , as a better overall fitness allows for better performance and thus increases long - term motivation .
interestingly , saar and jrime   showed such an association between sports participation and fitness only in adolescents , but not in children . in this study
it should also be considered that younger children generally display lower engagement in organized sports   and obtain most of their exercise via unstructured play .
.   argue that especially participation in vigorous activity increases physical fitness , but such activities can occur in unstructured play or general physical activity as well .
further , it could be argued that a prolonged engagement in sports is necessary to cause changes in physical fitness , and particularly in younger children , some may have just started participating in organised sports and , therefore , might not display any adjustments .
it should also be considered that the directionality of the relationship between regular sports participation and physical fitness can not be determined via a cross - sectional study .
it may be possible that children with a higher physical fitness are more likely to participate in organized sports due to their better abilities .
similarly , it remains to be determined whether increased body weight is a result of a lack of sports participation or whether selection bias leads to a lower participation of overweight children in organized sports .
most likely the association between sports participation and physical fitness as well as body composition is bidirectional , which will make it difficult to establish a causal pathway even in longitudinal studies .
nevertheless , it has been argued that participation in sports is one way to increase fitness and reduce body fat [ 33 , 59 ] even though biological and genetic aspects need to be considered .
in addition to the cross - sectional design other limitations of the present study should be addressed .
relying on parent questionnaires for children 's participation in organized sports may have introduced potential bias , particularly as parents were informed about the intention of the study due to the following intervention .
there is also no information on the intensity children experienced during training sessions or the duration of their training . in general , however , training in organized sports at this age lasts between 60 and 90 minutes per day .
further , only participation in organized sports was considered rather than total physical activity , which may be problematic , especially in younger children .
, however , did show a direct relationship between sports participation and habitual pa in preschoolers .
the large sample size , on the other hand , is a strength of the present study , and an analysis of missing value did not show any systematic bias .
in addition , anthropometric as well as physical fitness measurements were performed by trained staff and followed standard procedures , which adds to the credibility of the study .
  overall , the present study shows that increased participation in organized sports is associated with increased physical fitness and lower risk for overweight in elementary school children .
even though directionality of these relationships can not be established , these results emphasize the necessity for an early establishment of an active lifestyle , including sports participation , to allow for the development of various components associated with physical fitness as this may facilitate long - term engagement in sports and physical activity . considering the low levels of physical education in school with the continued risk of further reduction
, the promotion and facilitation of engagement in organized sports would be an important aspect concerning public health .
in germany , roughly 70% of boys and 65% of girls engage in organized sports , which could significantly contribute to children 's overall physical activity levels as long as sufficient activity time and engagement are assured .
in addition , participation in organized sports has been positively associated with the development of psychosocial components such as increased self - esteem , better stress tolerance , and reduced social isolation . these benefits along with the association between sports participation and body weight underline the importance of organized sports in a child 's development .
therefore , the facilitation of access to various sports that allow children with different abilities to engage in a variety of activities is a crucial aspect in today 's efforts concerning public health .
 physical inactivity is associated with poor physical fitness and increased body weight . 
 this study examined the relationship between participation in organized sports and overweight as well as physical fitness in primary school children in southern germany . 
 
 height , weight , and various components of physical fitness were measured in 995 children ( 7.6  0.4 years ) . 
 sports participation and confounding variables such as migration background , parental education , parental body weight , and parental sports participation were assessed via parent questionnaire . 
 multiple logistic regression as well as multivariate analysis of covariance ( mancova ) was used to determine associations between physical fitness , participation in organized sports , and body weight . 
 
 participation in organized sports less than once a week was prevalent in 29.2% , once or twice in 60.2% , and more often in 10.6% of the children . 
 overweight was found in 12.4% of the children . 
 children participating in organized sports more than once per week displayed higher physical fitness and were less likely to be overweight ( or  =  0.52 , p < 0.01 ) . 
 even though causality can not be established , the facilitation of participation in organized sports may be a crucial aspect in public health efforts addressing the growing problems associated with overweight and obesity . 