"About 50 percent of adult onset weight change remains genetic," says James C. Romeis, Ph.D., professor of health services research at Saint Louis University School of Public Health and the principal investigator of the study.
Romeis studied sets of twins who served in the military during the Vietnam War, some with identical and some with fraternal genes. He found that genes account for more than 50 percent of the change in Body Mass Index.
How we deal with our environment - what we eat, the amount we eat and how much we exercise - accounts for the other 50 percent, Romeis says. "You've got this genetic thing working against you that helps to explain why you're so heavy and why you may fail at diets and weight loss programs."
Romeis studied nearly 8,000 male twins at enlistment during the late 1960s, who now are married, well-educated, employed and middle-class. In early adulthood, more than 75 percent were of normal weight. Twenty years later, more than 55 percent were overweight or obese.
"Weight gain appears to increase gradually," Romeis says. "For these guys, it's at about 30 years old. Your behaviour changes at 30, you become more sedentary. At some point they tip into being overweight. Those who are overweight tip into becoming obese. It's slow, incremental change. At the same time, we didn't see much evidence that they lost weight during the same time period."
Romeis speculates that our increasingly sedentary, "super-size-it" lifestyle is particularly problematic for those who are at genetic risk of becoming fat. Genetics helps to explain the difficulty these men have at maintaining a normal weight, but it doesn't excuse it, Romeis says.
"Losing weight is going to be a lot of work for these guys," he says. "Treatments and public health interventions need to recognize the magnitude of genetic factors if short-term and long-term interventions are to be effective."
MEDICA.de; Source: Saint Louis University