A new study shows that obesity and the way fat is distributed on the body may be more related to a person's genes than previously known.

Experts at Boston's Joslin Diabetes Center said recently that important genes in the body's mechanics that regulate normal development seem to control obesity and body shape.

"By looking at your genes, we can tell how fat you are and how your body fat will be distributed," said lead researcher Dr. C. Ronald Kahn, the center's president and professor at Harvard Medical School. "In lower animals, it's long been known that genes play an important role in the body's development. Genes tell the body where the head goes and where the tail goes, what goes on the front and what goes on the back. In insects, genes determine if the wings go on the front or back and whether they will be large or small.

"So it's not surprising that in humans, genes may determine how many fat cells we have and where they are located."

Together with Joslin post-doctoral fellow Dr. Stephane Gesta and colleagues at the University of Leipzig in Germany, researchers for the first time used gene chips as a tool to understand what genes might control the development of fat inside the abdomen versus fat under the skin. The resulting study were published online April 10 and in the journal Proceedings of the National Academy of Sciences.

'Distinct' gene expressions

Location of fat on the body can affect a person's risk for developing chronic diseases. Doctors have long recognized that people who are "apple-shaped" - with fat concentrated in the abdomen - are at much higher risk for diabetes and metabolic syndrome than those whose fat is mainly subcutaneous, or distributed beneath the skin in the buttocks and thighs.

While recent studies at Joslin and elsewhere have shed light on the role of appetite and physical activity in obesity, little is known about the role of genes in fat distribution or the association of genes in disorders like type 2 diabetes.

To investigate, researchers examined the genetic makeup of fat samples from around internal organs and under the skin of  mice and nearly 200 humans ranging from normal to very obese. The human patients included people with mostly abdominal obesity and others with subcutaneous fat.

The researchers discovered that as many as 12 developmental genes may play a role in different fat deposits and that at least three seemed to be especially important in obesity.

"The differences we found in gene expression were so distinct that we could identify the level of obesity and the waist/hip ratio, or whether the fat is in the abdomen or under the skin, in the overweight population," Gesta said. "While we don't know yet whether this genetic activity is a cause or an effect of obesity, these data do suggest that different forms of obesity could be a developmental problem that begins very early in life."

Outsmart fat cells? 'No magic bullet'

Kahn, meanwhile, added that experts wonder if people can "outsmart" their fat genes to alter the outcome. Health experts said that inheriting big hips and big bellies shouldn't keep people from eating right and exercising to lose weight and shape up as much as possible to avoid chronic diseases and dying early.

"While we now can predict the fat pattern, we have no magic bullet to alter the outcome," Kahn said. "But with these new findings, we have identified potential targets for perhaps one day changing body shape. We don't have drugs to alter the pattern now, but perhaps in the future we will."