According to researchers in Boston, it is not just the types of foods consumed and a lack of physical exercise that lead to obesity; their findings suggest that both body shape and obesity could be controlled by our genes.
The research, published online yesterday in the journal Proceedings of the National Academy of Sciences, was conducted by scientists at Joslin Diabetes Center in Boston together with colleagues at the University of Leipzig in Germany.
"By looking at your genes, we can tell how fat you are and how your body fat will be distributed," said lead researcher Ronald Kahn, president of Joslin and the Mary K. Iacocca Professor of Medicine at Harvard Medical School.
In lower animals, he added, it has 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," he said.
Although it is well known that obesity is a major risk factor for type 2 diabetes and heart disease, the particular location of body fat can also significantly impact people's risk of developing serious chronic diseases.
Scientists have already revealed that people with abdominal obesity run a higher risk of developing diabetes and metabolic syndrome than those whose fat is mainly subcutaneous, or distributed beneath the skin primarily in the buttocks and thighs.
The Joslin scientists now claim to be the first to have 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 researchers examined the genetic makeup of fat samples from around internal organs and under the skin of both mice and almost 200 human subjects ranging from normal to very obese.
Theorizing that fat distribution patterns - and perhaps obesity itself - may originate in the genes involved in control of development, the researchers found that as many as 12 developmental genes may play a role in different fat depots and that at least three of these seemed to be especially important in obesity.
The researchers compared levels of activity for these three genes in intra-abdominal and subcutaneous fat taken from individuals of normal weight versus overweight or obese individuals.
"The differences we found in gene expression were so distinct that we could identify the body mass index (level of obesity) and the waist/hip ratio (whether the fat is in the abdomen or under the skin) in the overweight population by the expression level of these genes. This finding suggests that the expression of these genes could be related to the pathogenesis of obesity," said researcher Dr Gesta.
Indeed, just last month another study conducted by scientists at Duke University Medical Center revealed that obesity could be linked to a person's genes through the type of diet consumed by their mother during pregnancy.
The research claimed that a mother's consumption of a particular soy nutrient- genistein- elicits changes in an embryo's gene behavior that can later reduce the risk of obesity.
Mice fed diets rich in the soy component genistein gave birth to pups that remained slimmer as adults. According to the scientists, control group mice that did not receive prenatal genistein were double the weight of their genistein-fed counterparts.