Do Thin Parents Pass On Skinny Genes?

Study suggests thinness, like obesity, has genetic roots.

ByABC News
October 5, 2011, 11:57 AM

Oct. 6, 2011— -- People with thin parents are more likely to be thin themselves, a new study has found. But don't go chalking up weight woes to bad genes just yet.

Researchers from University College London in the U.K. studied more than 4,400 families with more than 7,000 children. Kids with two thin parents were twice as likely to be thin themselves compared to kids with two parents at the heavy end of a healthy weight range. And kids with overweight or obese parents were progressively less likely to be thin.

"We found evidence of a strong family association, with most thin children and adolescents coming from families in which both parents were thinner than average," the researchers reported in the October issue of Archives of Pediatric and Adolescent Medicine.

Previous studies have uncovered a similar trend at the other end of the scale: kids with overweight or obese parents are more likely to be overweight. Some studies have even implicated specific genes. But experts say genes alone can't explain the drastic rise in obesity over the past 30 years.

"Have our genes changed enough to account for this? Absolutely not," said Dr. David Katz, director of the Yale University Prevention Research Center. "But certain genes could account for the fact that some people are more vulnerable than others."

We share more than just genes with our parents, Katz said, adding behaviors like diet and exercise habits as well as education levels to the list.

"The distinction between nature and nurture in a study like this is absolutely impossible," Katz said. "You can break away from your family pattern if you behave differently than your family did."

Family history can provide helpful insight into risk factors for certain conditions, such as obesity, heart disease and diabetes. But family history is not destiny, Katz said.

"We have a major influence on our medical destiny in how we choose to live every day," he said. "Your genes may make you less vulnerable to weight gain, but anyone can gain weight."

Obesity rates are projected to soar in the coming years -- a dire forecast attributed to unhealthy diets high in processed foods and sedentary lifestyles. Katz likened the obesity "epidemic" to the Titanic.

"You could probably reach all sorts of genetic conclusions as to why some people got wet before others," he said, describing the different populations of people on various levels of the ship. "But the ship was sinking, so ultimately everyone was going to get wet."

Katz said people should focus on what they can do to stay healthy.

"Having a sort of, 'Oh, woe is me, there's nothing I can do about it' attitude is just wrong," he said. "Adhering to a basic pattern of healthful eating and activity is quite powerful."

But some people struggle with losing weight and keeping it off, making it harder to stay active. Katz said genetics could be at play, and created the National Exchange for Weight Loss Resistance -- an online community that lets users share tips and participate in research.

While scientists continue to study the heredity of weight woes, parents can help keep kids on track by setting a good example.

"The example that the parents set and the environment in which you live are very strong determinants of obesity or thinness," said Lisa Cimperman, a registered dietician at UH Case Medical Center in Cleveland. "The sooner we get kids on the path toward eating healthy foods, the more likely they are to carry that on into adulthood."

While genetics do play a role in body weight and shape, they're not the "be-all, end-all," Cimperman said.

"Being healthy is a choice, not something handed to you in your genes," she said, adding that thinness does not necessary go hand-in-hand with health.

When it comes to weight loss, there's strength in numbers. So support from the family you share genes with can boost your chance of success. Agree to eat more veggies, get rid of snacks or go for nightly walks as a team, Cimperman said.

"If you're trying to lose weight, chances are others in your family could improve their diets as well."