Cuypers et al. BMC Public Health 2012, 12:820 http://www.biomedcentral.com/1471-2458/12/820 imagine that in adolescents, a psychological susceptible period with diverse psychosocial influences and with peers as important reference persons, it might be diffi- cult to sustain a good self-concept. Adolescents without good self-concept might change easily their lifestyle to the unhealthier one of their friends. Modification of obesity-susceptibility genetic markers There is growing evidence that the 32 loci robustly asso- ciated in large-scale meta-analyses of GWAS with BMI in adults [25-27,29-31,36], also affect BMI in childhood and adolescence [31,32,54,55]. Heritability of BMI is esti- mated to vary from 0.58 among 11 year-old girls and boys to 0.83 and 0.74 respectively in 17 year-old boys and girls. Also, the genetic contribution to BMI seems to be strong during adolescence [56]. Though, the known combined genetic effect on BMI is modest, estimated to only 2–3 % of the genetic variation in BMI. In concordance to other studies [57,58] we preferred to use a genetic predisposition score rather than a single locus because a genetic predisposition score explains also a greater genetic variance. This approach may be prefer- able when demonstrating an interaction between genetic susceptibility and a life style factor. Additionally, multiple allele scores increase statistical power and may represent a more generalizable influence of genetic obesity suscep- tibility compared with analyses of individual variants. For estimating the cumulative effect of the SNPs com- bined we calculated a genetic predisposition score (GPS) by summing the BMI-increasing alleles across the 12 SNPs [35]. We did not weight the risk alleles on basis of their individual effect sizes because no well-accepted ef- fect sizes were available for each of the SNPs. It is previ- ously demonstrated that weighting of risk alleles may have limited effect [59]. Lajunen et al. [56] also indicated that common envir- onmental factors had an effect in early adolescence. According to Haberstick et al. [60] the role of environ- ment compared to genetic influence may be more pro- found in girls than in boys. Our data revealed a marked divergence between girls and boys in the distribution of body fat. Participation in social activities was in girls more related to central adi- posity and in boys to overall adiposity. This is in congru- ence with other studies [5,45]. The divergence between girls and boys may be due to biology which is expressed in differences in distribution, storage and metabolic pro- cessing of body fat. Physical activity in contrary to cul- tural activities seems not to attenuate the effect of obesity-susceptibility genetic variants on adiposity esti- mates in adolescents [61]. Eventually, environmental influences like psychosocial stress may override genetically driven factors [62] and increase particularly the central adipose measures in Page 8 of 10 girls, who are more susceptible for stress-related path- ology [63]. Another reason could be that the effects of genetic influences could be sex-limited due to different neuro-endrocrine functioning and fat metabolism [64]. As a consequence, an important question is whether this difference in fat distribution might be an indication of greater health risk in girls [64]. Further, from previous studies we know that the MC4R has a role in the food intake, thermogenesis and loco motor activity [65]. The well-known FTO has pos- sible a role in the HPA-axis and influences body com- position through energy expenditure [31,66,67]. Thus, a pathway that affects body composition through the cen- tral or distal nervous system might be possible. This pathway we have hypothesized also to be important for the effect of leisure time activity. Conclusion Both cultural and social leisure time activities in adoles- cence seem to have an effect on weight development into adulthood, but in opposite directions. In girls, par- ticipation in cultural activities seemed to protect against excessive weight gain, while participation in social activ- ities may increase overweight in both gender. This study is the first, to our knowledge, to indicate that the cumu- lative effect of obesity-susceptibility genes for obesity in girls and boys may be attenuated by participation in cul- tural activities. Additional file Additional file 1: Table S1. Genotype information and quality control statistics for the 12 obesity-susceptibility SNP. Table S2 Characteristics of baseline adolescent population who met the inclusion criteria and participated in the follow-up study as adults. Prevalence in numbers or percentages (%), distribution in mean and standard deviation (SD). Table S3 Characteristics of follow-up population who met the inclusion criteria and participated in the baseline study as adolescents. Prevalences are expressed in percentages (%), distribution in mean and standard deviation m (SD). Table S4. Associations between the index for cultural activities at baseline and the z-scores of body mass index (BMI), waist circumference (WC) and waist hip ratio (WHR) eleven years later as adults. Employed GEE linear type model. (N: all 1450 adolescents). Table S5. Associations between the index for social activities at baseline and the z-scores of body mass index (BMI), waist circumference (WC) and waist hip ratio (WHR) eleven years later as adults. Employed GEE linear type model. (N: all 1450 adolescents). Table S6. Associations between the index for cultural activities (without TV-viewing) at baseline and the z-scores of body mass index (BMI), waist circumference (WC), and waist-hip ratio (WHR) eleven years later as adults. Employed GEE linear type model. (N: 1123 normal-weight adolescents). Competing interests The authors declare no competing interests or any financial interests. Authors' contributions All authors have participated in the development and writing of this study. All authors read and approved the final manuscript.