Pear Shaped Genes

November 12, 2012

Pear Shaped Genes

A newly published report in the peer-reviewed journal Nature Genetics has led theDaily Express to report that a lady’s shape is all down to her genes. This according to a large scale study involving 200,000 people who were investigated in 61 separate studies. “Curvy women can ditch the diet – after scientists found that a woman’s body shape is all down to her genes”, reported the Daily Express. Except that it is not all together true, genetics can have a bearing on shape but other factors such as eating habits and the amount and types of exercise taken can all have a bearing on a person’s shape.

DNA from14 areas were identified as having an association with a person’s waist-to-hip ratio. One of these 14 had already been identified through earlier research. Because the pool of data was so large, 200,000 people, the detection of points where only a small effect on waist to hip ratio was seen could be identified. These areas account for only 1.03% of the differences seen between people involved in the study.

Previous studies suggest that genes may be responsible for between 22% and 61% of the variability in waist to hip ratio. Other genetic factors also have an input. In the future it is expected that the actual genes responsible for this attribute will be identified.

The study’s aim was to identify influential areas within the DNA and genes affecting the waist to hip ratio. It was a statistical pooling of a number of genome wide association studies. These studies compare one group’s DNA against another. By doing this variations can be identified. By have such numbers take part in the study means that genetic variations that have a small effect are more likely to be detected. So identifying characteristics which affect waist to hip ratios in each gene with an input can be easier in large scale studies.

The Genetic Investigation of Anthropometric Traits (GIANT) group carried out the research after funding was made available by charitable foundations, some governmental bodies and private companies.

Some newspapers and areas of the media make claims that cannot be substantiated. The study has only identified some locations where genes having a bearing on waist to hip ratio may be. They have not identified the actual genes. The researchers also say that only a small amount of variability of waist to hip ratio is controlled by these locations.

Method of Research

The researchers made the comparison of 32 case studies having 77,167 people involved, with a second group of 29 studies consisting of 113,636 participants. The whole system works by comparing a group of ‘cases’ versus a group of ‘controls’. Initially the researchers investigated instances of whether an individual had more or less variations than the controls. The genetic make ups of these cases were then compared with the second group to confirm initial findings. After this the two sets were combined to check for associations common to both sets. This gave an indication of strength of association.

The research only dealt with people of European descent to exclude the risk of different ethnicities influencing results. Age and body mass index (BMI) were also allowed for. Researchers also investigated whether women had different variations of waist to hip ratios because of the way women and men store fat differently.

Results

Fourteen areas in the DNA that contained variations related to waist to hip ratio were identified. After this, testing against the second group of 113,636 people took place. The results confirmed that 14 areas of DNA had genetic variations related to waist to hip ratio.

One location had already been identified in earlier research but the other 13 were new findings of genetic variations associated with waist to hip ratio. These variations all had a strong association to waist to hip ratio when all 61 studies were combined.

The locations of these genes were in or located in the proximity off genes whose roles include insulin reporting, controlling the activity of enzymes that break down fat and make fats. The locations identified were responsible for 1.03% of the variability seen in waist to hip ratio. The individual influences on variability of each location ranged from 0.02% up to 0.14%. Seven locations showed more effect in women in relation to waist to hip ratio. Body mass index was only influenced by 4 locations.

Conclusion

It was concluded that the findings prove that body fat distribution is affected by many genes. It also displays different behaviour in each sex and has no effect on the actual amount of body fat present. Waist to hip ratio affecting genes have been identified in a number of areas. However not all of the factors affecting waist to hip ratio have been identified. It is only known that 1.03% variability in waist to hip ratio has been identified. Other studies suggest that genetic factors may be responsible for between 22% and 61% of waist to hip ratio. This means that other genetic factors are yet to be found.

Because of the link between heart disease and body shape it is expected that further studies will take place. Fat distribution genetics must be better understood before the aims of preventing obesity and its related risks of heart disease can be achieved.

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