The genetics of obesity.


Sorensen TI.






Genetic and environmental factors both affect the development of human obesity. The prevalence of obesity has increased over the past 30 years, and changes in the environment must have played a key role in this increase. Studies of monozygotic twins have found differences in body weight that must be due to environmental influences. However, there is also considerable evidence suggesting a genetic basis for obesity. The body mass index (BMI) of adult offspring is correlated with the BMI of parents, and this can be entirely ascribed to the transmitted genes. Thus, the similarity of BMI is about twice as great among monozygotic twins as among dizygotic twins. Moreover, adoption studies have shown a correlation between the BMIs of biological parents, siblings, and adult adoptees, while the BMI of the adult adoptees showed no correlation with the BMI of their adoptive parents. A few major genes may contribute to the development of obesity. Genetic linkage and candidate gene studies have attempted to identify the genes involved in determining BMI in humans, but have so far produced mixed results.