Does genetics affect weight loss? To what extent?

Yes. The role of genetics in weight control has been carefully studied. There are some important lessons we can learn from the studies.

The most important lesson is that most weight gain is not entirely genetically determined. Within one family (even among identical twins) we often see one person who is very overweight and another who is not. By the best estimates available, genetics account for somewhere between 20% and 30% of excess weight (1). Of greater importance are familial and cultural habits related to food choices; for example, frequency of eating out, and portion size when eating at home.

Another lesson: Genetics are not invincible. There are numerous examples of individuals who have “overcome” what appeared to be a genetic predisposition for obesity. Calories consumed and calories burned still play the predominant role in determining our eventual weight and body size.

Losing, and even maintaining, weight requires considerable effort and sacrifice for most people. We all know someone who can eat whatever they feel like, exercise infrequently, and yet remain thin. This is usually due to a difference in metabolism which may also exist in others within the same family though not always.

In the end, learning how to eat better, move more, and stress less are the cornerstones to losing and controlling one’s weight. With some genetic backing, the tasks may be a little easier or more difficult, but no less necessary.

(1) Bouchard, C. Human variation in body mass: evidence for a role of the genes. Nutr Rev. 1997;55(pt 2):S21-S30