How DNA is packaged in human fat cells could be the reason why humans became fatter than their closest primate relatives, new research has shown. Whilst the healthy range for human body fat percentage lies between 14% and 31%, other primates have body fat percentages lower than 9%. The genetic reasons behind this difference could lead to a new genetic treatment for weight loss.

There are two types of fat in our body, white fat and brown fat. White fat acts as a major energy store and is the main culprit behind weight gain and obesity. Brown fat also stores energy but can easily release it, usually to generate heat to keep us warm. Both humans and chimpanzees have genes that enable the conversion of white fat to brown fat, but interestingly these are more accessible in chimpanzees than humans.

DNA can be stored in cells in either its condensed or uncondensed form. The uncondensed form allows genes to be expressed in the cell, whilst the condensed form prevents the gene from being expressed. Researchers studied 780 DNA regions which are responsible for white to brown fat conversion in both humans and chimpanzees. The ATAC-seq technique was used to determine if the genes were in their condensed or uncondensed form. It was found that the genes for converting white fat to brown fat were much more likely to be found in the condensed form in human fat cells but uncondensed in chimpanzee fat cells. Chimpanzees can therefore easily convert white fat to brown fat, which stops them from getting fat, whilst humans are less able to do this.

There may be an evolutionary explanation for this phenomenon. The human brain is three times the size of a chimpanzee brain and requires a huge amount of energy to operate. When the modern humans were evolving, increasing brain size gave them a clear survival advantage over their competitors. Therefore, it is advantageous for humans to have a higher proportion of white fat to provide the energy to allow the formation of a larger brain.

More research is undergoing to see if white fat can be converted to brown fat within the human body. If successful, this could be developed into a genetic treatment to aid weight loss. There is already evidence that people’s weight loss can be improved by taking the right diet for their genetic makeup.1 Together, these findings represent a move towards more personalised and effective solutions for weight loss.

1. Stanford and Interleukin Genetics inc. ‘Genotype Patterns Predict Weight Loss Success: The Right Diet Does Matter’ at the American Heart Association’s Joint 50th Cardiovascular Disease Epidemiology and Prevention, Nutrition, Physical Activity and Metabolism conference, March 2-5, San Francisco