To date, association studies have largely been restricted to candidate genes whose dysfunction might reasonably be expected to result in obesity by virtue of their having putative effects on energy intake, energy expenditure or nutrient partitioning. Genome-wide association studies are still in the future. The interpretation of association studies always requires caution because of the possibilities of problems such as population stratification, small sample size and publication bias. Some of these problems are exemplified by a common polymorphism in the b3-adrenergic receptor, where despite over 40 association studies, involving more than 7000 subjects, the findings have been markedly inconsistent (Barsh et al., 2000). While significant and consistent associations have been obtained in large case-control studies for some variants including the insulin VNTR (Le Stunff et al., 2001) and IGF-1 SNPs (Hart et al., 2004), it is true to say that as of now, no single common variant is widely accepted as unequivocally associated with an alteration in human adiposity. A comprehensive and updated reference for all association studies in obesity genetics is available in the form of the obesity gene map established by
Bouchard, Chagnon, Perusse and colleagues at The Pennington Biomedical Research Centre (link to www.obesite.chaire.ulaval.ca/genemap.html).
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