Fat distribution in our bodies depends on our genes, say researchers. Genetic factors influence whether fat storage occurs more in the trunk or other parts of the body. In other words, our genes determine whether our bodies have a pear or apple shape. The genetic effect is starker in women, scientists from Uppsala University reported.
The researchers wrote about their study and findings in the journal Nature Communications (citation below). The authors were Mathias Rask-Andersen, Torgny Karlsson, Weronica E. Ek, and Åsa Johansson. They are all from Uppsala University in Sweden
The authors measured the fat distribution of 360,000 individuals; all of them were voluntary participants.
Men and women store fat differently
Lead author, Dr. Mathias Rask-Andersen, a Postdoctoral Researcher at the Department of Immunology, Genetics and Pathology, said:
“We know that women and men tend to store fat differently – women have the ability to more easily store fat on the hips and legs, while men tend to accumulate fat around the abdomen to a higher extent.”
“This has been attributed to the effects of sex hormones such as estrogen. But the molecular mechanisms that control this phenomenon are fairly unknown.”
Measuring fat distribution
The research team gathered and analyzed data from the UK Biobank. The UK Biobank is a long-term British biobank study which is investigating the contributions of genetic predisposition and environmental exposure to disease development. The study comprises half-a-million volunteer participants in the United Kingdom.
The participants had given blood samples for genotyping. The authors estimated fat distribution using impedance measurements. Impedance is the resistance to the flow of an alternating current (electrical current). They measured the level of resistance when electricity traveled through the body.
The authors tested millions of genetic variants across the genome. They were looking for associations with fat distribution, specifically to the legs, arms, or trunk (abdomen).
The team identified almost one hundred genes that affect fat distribution to different parts of the human body. They also detected a high degree of heterogeneity between men and women. In other words, they detected ‘ typically male characteristics,’ which were different from ‘typically female characteristics,’ and vice-versa.
Genetic effects on women
Co-author, Åsa Johansson, an Associate Senior Lecturer at the Department of Immunology, Genetics and Pathology, said:
“We were struck by the large number of genetic effects that were stronger, or only present, in females. Upon closer examination, several of the associated genes were found to encode proteins that actively shape the extracellular matrix, which makes up the supporting structure around cells.”
The findings suggest that a mechanism that generates differences in body fat distribution is in the remodeling of the extracellular matrix. It is probably one of several mechanisms.
Fat distribution – apple or pear shape
Studies have shown that people who have an apple shape have a higher risk of disease than individuals with a pear shape.
If fat accumulates around the abdomen (trunk), your body has an apple shape. Fat accumulation around the hips and limbs gives people a pear shape.
Fat distribution in men tends to be different from women. Men have more abdominal fat than women. This could explain why males are more likely to develop cardiovascular diseases than females.
Some studies have even shown that having a pear shape might protect against developing cardiovascular diseases.
Uppsala University, in a press release, made the following comment regarding this latest study:
“The result of the current study may, therefore, lead to the development of new interventions to reduce the risk of cardiovascular disease.”
Regarding their findings, Dr. Rask-Andersen said:
“The biological systems we highlight in our study have the potential to be used as points-of-intervention for new drugs that are aimed at improving the distribution of body fat and thereby reducing the risk of disease.”
“Genome-wide association study of body fat distribution identifies adiposity loci and sex-specific genetic effects,” Mathias Rask-Andersen, Torgny Karlsson, Weronica E. Ek, and Åsa Johansson. Nature Communications, volume 10, Article number: 339 (2019). DOI: https://doi.org/10.1038/s41467-018-08000-4.