Genetic susceptibility to an obesogenic environment
Roughly 70 percent of obesity risk is genetically inherited; however, this genetic inheritance is best understood as a susceptibility to a fattening environment––i.e. in a healthy environment, genes alone do not usually cause obesity: in an unhealthy environment, genetically susceptible people become obese, while others remain lean because they are not genetically susceptible. [1]
- The physical and psychological drivers inherent in human biology mean that the vast majority of people are predisposed to gaining weight. We evolved in a world of relative food scarcity and hard physical work rather than the modern world, where energy-dense food is abundant and labour-saving technologies and sedentary life patterns abound. [5]
- The predisposition (by phenotype) to lay down fat is an evolutionary genetic legacy; with the GAD2 gene (on chromosome 10, human genome) appearing to interact with, and speed up, brain neurotransmitters, which in turn activate part of the hypothalamus, stimulating people to eat more. [6]
- However, moving from a genetic predisposition to obesity itself generally requires some change in diet, lifestyle, or other environmental factors. [7]