Although genetic factors fundamentally govern susceptibility to atopic disease, increases in atopy have occurred within too short a time frame to be explained by a genetic change in the population, thus pointing to environmental or lifestyle changes.[61

Although changes in the genetic makeup of populations occur too slowly to be responsible for this rapid rise in obesity, genes do play a role in the development of obesity.
identical twins are likely to have the same allergic diseases about 70% of the time; the same allergy occurs about 40% of the time in non-identical twins.[23]
The estimate of heritability of both BMI and waist circumference was 77%. Thus, in the midst of the obesity epidemic, the evidence that hereditary factors are important remains unassailable.
Allergic parents are more likely to have allergic children,
Studies on large populations of adopted children show that there is no relationship between body weight and adoptive parents, but a close correlation with biological parents.