Binge-eating not solely caused by poor willpower, a weak gene helped:
study

       Mar. 20, 2003  
       
       
Provided by: Canadian Press    
       
Written by: JEFF DONN  
       

BOSTON (AP) - Binge-eaters who say they can't help it may be right.

A study suggests a weak gene, not feeble willpower, may be the cause
for some people. The research may point the way to a future pill to
tame their appetites.

The joint Swiss-German-American study makes the strongest case yet
that genetic mistakes can cause an eating disorder, researchers
say. Traditionally, eating behaviour has been viewed as complex and
cultural in its causes. "Willpower is not always important to reduce
weight. Some people can by willpower. Some cannot, and I think these
patients have a hard time," said Dr. Fritz Horber, the leader of the
binge-eating study at the Hirslanden Clinic in Zurich, Switzerland.

Researchers have been trying to understand the reasons for an epidemic
of obesity, which raises the risk for heart disease, diabetes and many
other ailments. About 30 per cent of American adults are obese, up
from 14 per cent 25 years ago, according to government data. The surge
is widely blamed on abundant high-calorie foods and sedentary
lifestyles.

However, some researchers have also begun to link several genes to
obesity, implicating heredity as an important underlying
factor. Increasingly, eating problems are thought to stem from a
subtle interaction of lifestyle and multiple genes.

Binge-eaters, who are usually but not always overweight, frequently
and compulsively stuff themselves - often in secret - and feel ashamed
afterward.

In this study, published Thursday in The New England Journal of
Medicine, the researchers focused on a gene linked to obesity in
earlier studies. Known as the melanocortin 4 receptor gene, it makes a
protein by that name that helps stimulate appetite in the brain's
hunger-regulating hypothalamus. If a mutated gene makes too little
protein, the body feels too much hunger.

The researchers considered 469 severely obese white adults - a quarter
of them binge-eaters. However, the disorder was much more common among
the five per cent with the mutated gene. All of them were
binge-eaters, compared to just 14 per cent of those with no mutated
gene.

In another study in the same journal issue, a British team reported
finding mutations of the same gene in more than five per cent of 500
severely obese children. The genetic link was so strong the
researchers could use results from chemical tests on their genetic DNA
to predict how much the children would eat at a meal.

Horber, the Swiss researcher, said other eating disorders, including
other types of bingeing, probably stem from a variety of genes and
environmental factors. However, he said the still-unnamed binge-eating
syndrome tied to this gene is especially important because it is
perhaps the most stubbornly resistant to dieting and exercise.

Horber said the binge-eaters in his study felt a wave of relief from
guilt when they learned of the genetic cause behind their
compulsion. Dr. Stephen O'Rahilly, one of the British study's
researchers at the University of Cambridge, said one family in that
study was so ecstatic over evidence of a physical cause that they made
themselves T-shirts saying, "We've got an MC4 mutation."

Eric Ravussin, a Louisiana State University researcher on obesity
genetics, said, however, that without more biochemical proof, he
remains "a little bit skeptical" that these mutations - and not others
located nearby on the same chromosome - are the syndrome's precise
cause.

But Dr. Joel Habener, a diabetes expert at Boston's Massachusetts
General Hospital who co-wrote an accompanying editorial, said the
Swiss-led study demonstrates either the "genetic cause or a very
strong association."

And he agreed with the researchers, who said future drugs acting like
the melanocortin 4 receptor protein may compensate for the genetic
defect. Habener said such chemicals are apt to be small molecules that
can be delivered as pills.