Humans and mammals possess two types of fatty tissue: white and brown.

The white fat tissue is what we see as "fat", that influences body shape and most people are bothered about.

The brown tissue, on the other hand, is a fat tissue whose role is that of burning fat, so that the energy from fats is released as heat in order to keep us warm (thermogenesis).

A team led by Barbara Cannon and Jan Nedergaard at the Wenner-Gren Institute, Stockholm University in Sweden, together with British and American researchers, have succeeded in proving for the first time that the two types of cells that become the so-called brown or white fat tissue have different embryonic origins, the kind of fat tissue they will be being set from the beginning.

"This is an answer to many years of discussion in the field, where two views have been put forward: that the cells can have two different fates, brown or white, or that they were predetermined to be one or the other, as this study now shows. An additional and highly unexpected finding was that it could be demonstrated that the very young cells that were to become brown fat cells had characteristics similar to those of young muscle cells," said Barbara Cannon, professor of physiology.

This finding elucidates the properties that primarily differentiate brown fat from white fat, like being able to burn fats, something that also happens in the muscle cells.

Researchers focus on the potential of brown fat to burn fat and thereby be involved in future methods of helping fat people get slimmer or fight against obesity. "Our findings do not exclude the possibility of influencing young cells to develop in one direction or the other. It also seems as if there are dormant brown fat cells within the body that could be stimulated to develop and become active, fat-burning cells. Normally adult humans are seen as having rather little brown fat tissue, but new studies using new technologies are starting to challenge this view. We see new potential for understanding the mechanisms that make cells develop into different tissues. And new knowledge always paves the way for new possibilities," said Cannon.