The percentage of obesity that can be attributed to genetics varies widely, depending on the population examined, from 6% to 85%,[6] with the typical estimate at 50%.
[30] The thrifty gene hypothesis postulates that due to dietary scarcity during human evolution people are prone to obesity.
[31] This is the presumed reason that Pima Native Americans, who evolved in a desert ecosystem, developed some of the highest rates of obesity when exposed to a Western lifestyle.
[32] Numerous studies of laboratory rodents provide strong evidence that genetics play an important role in obesity.
[41] In people with early-onset severe obesity (defined by an onset before 10 years of age and body mass index over three standard deviations above normal), 7% harbor a single locus mutation.