No. 7/25. October 2001
Embargoed until: Thursday, October 25, 2001, 12.45 pm
Obesity - Researchers go on a Gene Hunt
Homo sapiens not genetically suited to a Modern Lifestyle - Obese People should not be stigmatised by Society
The genetic programme that ensured the survival of our
forefathers in the stone age is clearly much less suitable for modern homo
sapiens. Hunter-gatherers were able to live off the fat their bodies stored up
in the good times when their food supply ran out but, nowadays, people normally
have enough to eat and do not have to go hungry. Improvements in living
conditions with a diet high in fat and a reluctance to take enough physical
exercise have, in the last couple of decades, led to millions of people in
developed countries in the West, and also in some developing countries, putting
on excess weight and even becoming obese. There has also been an increase in
the number of young children and teenagers who are overweight. The German
Society of Nutrition estimates that about one in every six children of school
age in the Federal Republic is too fat. However, according to Prof. Johannes
Hebebrand, a child psychiatrist and bioscientist at the University of Marburg,
our genes are at least partly to blame for this. “Our genetic profile is
unsuitable for a modern lifestyle. This means that obesity is also under
genetic control. This is shown by studies involving thousands of twins, adopted
children and families”, he claimed at a press conference on October 25, 2001,
held as part of the 2nd International Symposium on Obesity and Hypertension at
the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch (Germany).
In Berlin, Prof. Hebebrand gave some examples to illustrate his hypothesis about the effect of genetic factors on bodyweight. In a so-called over-feeding study in monozygotic (identical) twins, it was found that not all subjects put on the same amount of weight. In fact, the increase in weight ranged from 4.3 to 13.4 kilograms. However, both twins in a pair put on the same amount of weight. Women on a high-fat diet became markedly overweight if their first degree relatives were obese. If an infant is overweight this is not an immediate cause for concern, but it can lead to a risk of remaining fat in later life, if one or both parents are fat. Naturally, the degree of obesity plays a role: the more overweight the child, the greater the risk that he/she will be overweight in adulthood.
In addition to these findings, in recent years, researchers have obtained solid evidence to support their assumptions. They have been able to identify a number of genes which play a role in the regulation of bodyweight, initially in mice then also in humans. There is, for instance, the example of the leptin gene discovered in 1994. Under normal circumstances, it produces a hormone in fat cells which regulates the sensation of hunger. If it does not function correctly, then the person becomes severely overweight. In addition, various genes have been identified that can trigger different forms of obesity. The most common form of genetically-controlled obesity known to date, which is based on mutations in the so-called melanocortin-4 receptor-gene, is found in about two to four per cent of severely overweight people.
In the Marburg Clinic for Paediatric Psychiatry and Psychotherapy, in addition to looking at the genetic causes of obesity, Prof. Hebebrand and his colleagues are also actively engaged in its treatment. Prof. Hebebrand believes that the latest discoveries in genetics will lead to the development of potent drugs for obesity, a condition which has so far proved difficult to treat. “The fact that not only lifestyle but also a person’s genetic profile plays a role in the development of obesity will, hopefully, mean that people who are overweight will no longer be stigmatised by society”, he said.
Barbara Bachtler
Press and Public Affairs
Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch
Robert-Rössle-Straße 10; 13125 Berlin; Germany
Phone: +49 (0) 30 94 06 - 38 96
Fax: +49 (0) 30 94 06 - 38 33
e-mail: presse@mdc-berlin.de
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