Genetics
The causes of obesity are many, but there is little doubt that
genetic factors play an important role in its etiology. Humans
carry probably dozens of genes that are directly related to
body size. One of the specific roles for genes is the determination
of set points. Identification of such genes is important,
and several types of studies must be performed to address
this. Linkage analysis can be used to find physical locations
of genes that are relevant to a phenotype. If a specific gene
plays a role in the determination of a given phenotype, the
gene and the phenotype will be transmitted together (cosegregate)
across generations. The fact that the etiology of
obesity is so complex underscores the need for better understanding
of genetic determinants as a basis for more rational
interventions to treat obesity.
Several approaches have been used to search for specific
genes involved in obesity: identification of mutations responsible
for obesity in rodent models, association or linkage of
obesity measures with candidate genes in humans, and
chromosomal localization of genes by linkage of polymorphic
markers to obesity and related phenotypes in humans
and mice. To date, causative genes have been found for 5
obese mouse models. Two, leptin and leptin receptor,