Believe it or not, there are over 400 different genes that have been implicated in the contribution of weight gain! Genes contribute to the causes of obesity in many ways: by affecting appetite, satiety (the sense of fullness), metabolism, food cravings, body-fat distribution, and the tendency to use eating as a way to cope with stress.

The strength of the genetic influence on weight varies quite a bit from person to person. Research suggests that for some people, genes account for just 25% of the predisposition to be overweight, while for others, the genetic influence is as high as 70% to 80%.

So, how much of your weight depends on your genes? At this point, we do not have a specific test to determine how much our genetic composition influences our weight gain. However, your genes are probably a significant contributor to your weight gain if you have any of the following

characteristics:

• You have been overweight for much of your life.
• One or both of your parents have had problems with their weight. If both of your parents have obesity, your likelihood of developing obesity is as high as 80%.
• You can't lose weight even when you increase your physical activity and stick to a low-calorie diet for many months.

Why Do We Have these Genes?

When the crops failed or the prey escaped, how did our ancestors survive? Those who could store body fat to live off during the lean times lived, and those who couldn't, perished. This evolutionary adaptation explains why most modern humans — about 85% of us — carry so- called “thrifty genes,” which help us conserve energy and store fat. Today, of course, these thrifty genes are a curse rather than a blessing. Not only is food readily available to us nearly around the clock, we don't even have to hunt or harvest it!

Given My Genetics, What Can I Do to Lose Weight?

People with only a moderate genetic predisposition to be overweight have a good chance of losing weight by eating fewer calories and increasing their exercise level. These people are also more likely to be able to maintain their lower weight once they have lost it.

In contrast, people with a strong genetic predisposition to obesity may not be able to lose weight with the usual forms of diet and exercise therapy. Even if they lose weight, they are less likely to be able to maintain the weight loss. What I tell my patients is that, unfairly, they will have to embark on more aggressive treatment to combat the weight gain compared to others.

For people with a very strong genetic predisposition, sheer willpower is ineffective in counteracting their tendency to be overweight. Typically, these people can lose weight and maintain weight loss only under a doctor's guidance. They are also the most likely to require weight-loss medications or surgery for successful weight management. The good news is that there are more effective weight loss medications available to adults and children every year, and bariatric surgery has become much safer over the past decade.

The prevalence of obesity among adults and children in the United States has been rising since the 1970s. Therefore, genes alone cannot explain such a rapid rise. Although the genetic predisposition to be overweight varies widely from person to person, the rise in weight appears to be nearly universal, cutting across all demographic groups. These findings underscore the detrimental changes in our food supply and environment, which have contributed to the obesity epidemic.