News Release

Fat In Spite Of Hard Farm Work - Tracking Down Obesity

Peer-Reviewed Publication

Deutsche Forschungsgemeinschaft

Every second German is overweight. And every fifth German exceeds his normal weight by even more than 20%; this is what the medical profession refers to as pathological obesity or adiposity. Obesity is the cause of many sequellae such as hypertension, diabetes and cancer. So far little has been known about the factors supporting overweight. Is it genetic defects which impair the quick combustion of nutrients or do only those suffer from obesity who eat too much and too fatty a diet and don't get sufficient exercise to boot? That, in any case, the cause is not genes alone is what Trier scientist Dr. Petra Platte found out in a study funded by the Deutsche Forschungsgemeinschaft (DFG). She observed that genetic predisposition played indeed a major role in the development of obesity. But, she says, environmental factors such as eating habits and the extent and frequency of physical exercise are equally important.

Researchers had already shown that individual changes in the mouse genome can cause obesity. This discovery suggests that also in humans such mutations might be responsible for the disease. So far the search for a trigger gene has not yielded any results. Now scientists assume that in humans there has to be more than a genetic defect to cause obesity. Different fat distribution patterns ("apple shape" versus "pear shape") in humans must have different genetic causes.

Doing research for her habilitation thesis (research work prerequisite to obtaining a professorship) at the University of Trier, Petra Platte began to look for suitable subjects and finally found them at the east coast of the USA. This is where the Old Order Amish People live, a strictly conservative religious community whose ancestors in the 18th century immigrated from Germany and Switzerland mainly to the US states of Ohio and Pennsylvania. Even today the Amish are still cultivating a religious, ascetic lifestyle and strictly reject modern technology.

For Petra Platte it is clear that "the Old Order Amish People are probably the most homogeneous group world-wide for the genetic study of adiposity". For the Amish People have lived in genetic isolation since they immigrated from Switzerland and Germany. They marry only within the Amish community. All families, with an average of seven children, have the same socio-economic status and earn their living by farming. Their everyday life is dominated by hard manual labour, because instead of tractors they use mules, drive in carriages instead of cars and refuse to use electricity.

For the Amish obesity is ordained by God, and only stout men are considered suitable for hard work in the fields - thin women are believed to be infertile. The ideal of slimness which dominates the Western world is completely foreign to the Amish. This is why they do not diet to lose weight - an additional advantage for geneticists. Petra Platte also peeped into the pots of the Amish and found that they stuck to a traditional menu which includes eggs, meat, pasta, fatty sauces and cake on a daily basis. Given the hard farm work this diet should not necessarily lead to obesity. But the Amish become obese as frequently as the Germans who on average have much less physical exercise.

The scientist from Trier University spent three years in Lancaster County, Pennsylvania. It took more than a year before she had won the confidence of the Amish who live a secluded life. She recorded the weight of about 3,000 members of 17 extended families. The data were analysed to find clues as to whether specific families had a higher incidence of obesity and whether this could provide the basis for a heredity model. At first, similarities in body type within one family were studied. Fat Amish People indeed have mostly fat children and also fat siblings. Hence, obesity could have genetic causes.

Then the data obtained were compared with various genetic models based on Mendel's theory of heredity as well as with non-genetic models which assume an incidental occurrence of obesity in the case of higher food intake. But chromosomes are not the sole cause of obesity; overnutrition and a high-fat diet have to come in as additional factors. If, however, there is no genetic predisposition, even excessive food intake will much less frequently result in a manifestation of the disease.

Petra Platte, a psychologist, is now continuing her research. She was also able to take blood samples of the most suitable subjects which she is now subjecting to genome analysis. She hopes that the results will provide information on the loci involved in the genetic causes of obesity. Her habilitation thesis will be finished shortly.

For further information please contact

Dr. Petra Platte
Forschungszentrum für Psychobiologie und Psychosomatik der Universität Trier
Phone +49-651-946 2407
e-mail plattedr@aol.com

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