Public Health Perspectives

Genetic polymorphisms and Quantitative Trait Loci (QTLs) associated with specific obesity sub-phenotypes

Genotype-environment interactions arise when the response of a phenotype (e.g. fat mass) to environmental changes (e.g. dietary intervention) is modulated by the genotype of the individual.  Louis Perusse and Claude Bouchard 2000 (1)

For most overweight people, obesity is a product of gene-environment interaction.  This fact is no surprise to most of us, because we have observed that different individuals respond differently to the same environment.  This observation has been made about individuals and their tendency to gain weight.  In fact, among persons sharing an environment, genotype may account strongly for rank order of proportion of fat to lean body mass (2).  However, the relation between genotype and the susceptibility to gain weight is not simple or straightforward.  The genetic elements associated with obesity are seldom traced back to a mutation in a single gene.  Many genetic factors may contribute to obesity, but none of them are sufficient to account for any large proportion of the risk by themselves.  Also, an increased susceptibility to obesity is likely to result from more than one combination of genetic and environmental risk factors.

Variations in many genes have been found to be associated with different aspects of obesity.  The table below summarizes the reported associations between specific phenotypes of obesity and specific genes.  All of the associations listed below were reported to have p values of 0.05 or less (3).  The smaller the p value, the greater the likelihood that the association observed is due to a true relationship of some sort and not due to chance.  For more information on specific studies please see Perusse et al. 2001(3).

1. Perusse L, Bouchard C. Gene-diet interactions in obesity. American Journal of Clinical Nutrition 2000;72(supplement):1285S-90S

2. Hirsch J, Leibel RL. The genetics of obesity. Hospital Practice 1998;33(3):55-9,62-5,69-70

3. Perusse L, Chagnon YC, Weisnagel SJ, et al. The human obesity gene map:  the 2000 Update. Obesity Research 2001;9(2):135-69

4. Online Mendelian Inheritance in Man, OMIM (TM). McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University (Baltimore, MD) and National Center for Biotechnology Information, National Library of Medicine (Bethesda, MD), 2000.
   World Wide Web URL: http://www.ncbi.nlm.nih.gov/omim/

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This page last modified on October 05, 2004