***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: Obesity has a heritable component ; however , the heterogeneity of obesity complicates dissection of its genetic background . In this study , we therefore focused on eating patterns as specific traits within obesity . These traits have a heritable component ; genes associated with a specific eating pattern have not yet been reported at the population level . In this study , we determined whether genetic variations in cholecystokinin ( CCK ) and leptin genes underlie specific eating patterns . We selected obese individuals showing extreme snacking behavior or use of excessive portion sizes from a large population -based sample ( n = 17,357 ) from the Prospect -EPIC ( European Prospect i ve Study into Cancer and Nutrition ) study . Using allele-specific PCRs , we tested several single nucleotide polymorphisms in the c and i date genes and performed haplotype analysis . Obese carriers of common allelic variations in leptin or the leptin receptor gene had an increased risk to display extreme snacking behavior . In contrast , obese carriers of common allelic variations in CCK had an increased risk to eating increased meal sizes . In conclusion , we identified common allelic variants specifically associated with distinctly different eating patterns , namely extreme snacking behavior or excessive portion size Recent animal studies indicate that leptin is involved in the regulation of blood pressure through the leptin receptor . Therefore , 51-yr-old men ( N = 284 ) were selected ; and anthropometric , endocrine , metabolic , and hemodynamic variables were examined in relation to polymorphisms of the leptin receptor gene ( LEPR ) , by restriction fragment length polymorphism technique . Three polymorphisms were examined : Lys109Arg in exon 4 , Gln223Arg in exon 6 , and Lys656Asn in exon 14 . In comparison with Lys109 homozygotes , Arg109 homozygotes ( 9 % ) showed lower body mass index ( BMI ) and abdominal sagittal diameter , as well as lower systolic ( 10.0 mm Hg ) and diastolic ( 7.8 mm Hg ) blood pressure . Additionally , Arg223 homozygotes ( 26.8 % ) showed lower blood pressure ( 7.6/5.7 mm Hg ) than Gln223 homozygotes . These lower blood pressure levels were independent of other variables . No differences were found with the Lys656Asn polymorphism . Measurements of body fat mass correlated with leptin concentration in Lys109 homozygotes and in Lys109 heterozygotes but not in Arg109 homozygotes . Blood pressure correlated with leptin only in men carrying the wild-type allele Lys109 . With both elevated BMI and leptin , Lys109 homozygotes had higher blood pressure than the Arg109 homozygous men ( 12.4/6.9 mm Hg ) . Men with blood pressure  > or = 140/90 mm Hg had , in comparison with normotensive men , increased BMI and leptin levels , and Lys109 homozygotes were significantly more prevalent . These results suggest that leptin is associated with blood pressure regulation in men through the leptin receptor . When BMI and leptin are elevated , increased blood pressure is found only with the most prevalent LEPR genotype at codons 109 and 223 , whereas variants of this receptor seem to protect from hypertension . This might explain why not all obese men are hypertensive We performed extensive and realistic simulations of the colonization process of Europe by Neolithic farmers , as well as their potential admixture and competition with local Palaeolithic hunter – gatherers . We find that minute amounts of gene flow between Palaeolithic and Neolithic population s should lead to a massive Palaeolithic contribution to the current gene pool of Europeans . This large Palaeolithic contribution is not expected under the demic diffusion ( DD ) model , which postulates that agriculture diffused over Europe by a massive migration of individuals from the Near East . However , genetic evidence in favour of this model mainly consisted in the observation of allele frequency clines over Europe , which are shown here to be equally probable under a pure DD or a pure acculturation model . The examination of the consequence of range expansions on single nucleotide polymorphism ( SNP ) diversity reveals that an ascertainment bias consisting of selecting SNPs with high frequencies will promote the observation of genetic clines ( which are not expected for r and om SNPs ) and will lead to multimodal mismatch distributions . We conclude that the different patterns of molecular diversity observed for Y chromosome and mitochondrial DNA can be at least partly owing to an ascertainment bias when selecting Y chromosome SNPs for study ing European population 
    Output:
    
The meta- analysis of published data did not show an overall association between any of the tested LEPR variants and overweight .
However , the choice of a BMI cut-off value to distinguish cases from controls was crucial to explain heterogeneity in Q223R .
Differences in allele frequencies across ethnic groups are compatible with natural selection of derived alleles in Q223R and K109R and of the ancient allele in K656N in Asians .
In CoLaus , the rs10128072 , rs3790438 and rs3790437 variants showed interaction with sex for their association with overweight , waist circumference and fat mass in linear regressions .
Conclusions Our systematic review and analysis of primary data from the CoLaus study did not show an overall association between LEPR SNPs and overweight .