space_oddity said:
There is no gene that controls obesity. You cannot be predisposed to being overweight, regardless of metabolic rate or any other biochemical factor.
I believe obesity will be what early 21st century will be remembered for throughout history. Our descendants will read about a time when 1 in 2 children born in USA/UK/Australia will spend most of their lives clinically overweight, while globally, 1 in 5 people will live their entire lives in poverty.
No to the first paragraph, and yes to the second.
Warning: Wikipedia spam (read bolded for tl;dr)
"Like many other medical conditions, obesity is the result of an interplay between genetic and environmental factors. Polymorphisms in various genes controlling appetite and metabolism predispose to obesity when sufficient calories are present. As of 2006 more than 41 of these sites have been linked to the development of obesity when a favorable environment is present.[92]
Some of these include the FTO gene polymorphism and the NPC1 gene.[93] Adults who were homozygous for a particular FTO allele weighed about 3 kilograms more and had a 1.6-fold greater rate of obesity than those who had not inherited this trait.[94] This association disappeared, though, when those with FTO polymorphisms participated in moderately intensive physical activity equivalent to 3 to 4 hours of brisk walking.[95]
Another study found that 80% of the offspring of two obese parents were obese, in contrast to less than 10% of the offspring of two parents who were of normal weight.[96][9]
The percentage of obesity that can be attributed to genetics varies from 6% to 85% depending on the population examined.[97]
The thrifty gene hypothesis postulates that certain ethnic groups may be more prone to obesity in an equivalent environment. Their ability to take advantage of rare periods of abundance by storing energy as fat would be advantageous during times of varying food availability, and individuals with greater adipose reserves would be more likely survive famine. This tendency to store fat, however, would be maladaptive in societies with stable food supplies.[98] This is the presumed reason that Pima Indians, who evolved in a desert ecosystem, developed some of the highest rates of obesity when exposed to a Western lifestyle.[60]
Obesity is also a major feature in a number of rare genetic conditions: Prader-Willi syndrome, Bardet-Biedl syndrome, MOMO syndrome, leptin receptor mutations, congenital leptin deficiency, and melanocortin receptor mutations. In people with early-onset severe obesity (defined by an onset before ten years of age and body mass index over three standard deviations above normal), 7% harbor a single locus mutation."