Exercise Trumps Heredity

Studying identical twins is very important because they help scientists separate what has a genetic cause and what is caused by a person's environment or their lifestyle. Since their genes are the same, generally speaking health differences between the two individuals in a set of identical twins can be traced to lifestyle or environmental factors.

Every now and then I'll hear someone who is overweight say, "I can't lose weight. My whole family is overweight. It's genetic." An interesting article in the International Journal of Obesity (2009;33(1):29-36) says that while that may be true for some people, it doesn't appear to be an unavoidable fate.

Researchers in Finland kept track of all of the twins born in that country between 1975 and 1979. From 2000 to 2002 the twins were sent a health, diet and exercise questionnaire every six months. The questions included information on height, weight, and waist circumference, as well as how much the respondents exercised.

From those twins who responded, the researchers were able to look at the relationship between waist circumference, Body Mass Index, and exercise. They came to some very interesting conclusions:

For young adults, the more they exercised, the lower their Waist Circumference was. The researchers concluded that Waist Circumference was a better measure of obesity than Body Mass Index, especially for young healthy men. (Again, this is among young adults.)

Waist Circumference in general tended to be lower in those who exercised. This is important when you remember that those who carry their fat around their middle ("apple-shaped") are more likely to have heart disease.

They also discovered that for those twins who appeared to be genetically disposed toward overweight and obesity, the twin who exercised more tended to be leaner than their sibling twin who exercised less or not at all.

What this means for you

While you may well be genetically disposed to being overweight or obese, there is no excuse for not exercising if you are physically able to do so. Really out of shape? Start walking. Even a 5 or 10-minute walk is better than nothing, and if you do it consistently you'll be able to walk further and further. Small changes can make a big difference!

First posted: May 6, 2009