Genetics and Obesity
Although genetics and environmental factors do not "cause" obesity, they do increase a person's chances of becoming overweight or obese. Many researchers agree that environmental changes (such as the availability of food and a decrease in physical activity) have contributed to the rising numbers of obese people. However, genetics also plays a role.
We all have known that person who "could eat whatever they wanted to." In most cases, this person has been blessed with great genetics because what they burn on a daily basis (their metabolism or "calories-out") is a lot higher than it is for the average person.
But what about those people who burn less than the average person because of genetics? Does genetics cause obesity in these people? The answer to this question is no. Genetics is not a cause of obesity, but it can increase a person's chances for becoming overweight or obese (known as an obesity risk factor).
(Click Causes of Obesity for more obesity risk factors.)
Most obesity research scientists agree that the rising numbers of obese people is partially a result of major environmental changes that have occurred during the past few decades. Specifically, this includes the availability of food combined with a decrease in physical activity. As a result, many people consume more calories than they can burn, thereby gaining weight.
Obvious environmental changes have led people to think that a person's genetics have had little or nothing to do with the recent surge in obesity. Although it is unlikely that there has been a surge in the frequency of genes that predispose people to obesity, genetics does influence body weight. The ability to capture, circulate, and accumulate energy in the human body is so finely regulated that genetics must be involved.
Also, a tremendous diversity exists in the way that people are affected by environmental changes. For example, not all people living in industrialized countries are obese or will become obese. In addition, among the obese, the health consequences of obesity vary. This diversity occurs even among groups of the same racial or ethnic background, and even within families living in the same environment. All of these observations are consistent with the theory that obesity is influenced by genetic diversity interacting with environmental changes.