Your Number of Fat Cells Is the Same Since Adolescence

Whether you look like Peter Doherty or Michael Moore, there is a fixed number of fat cells in your body since adolescence, as revealed by a new research published in the journal Nature and carried out at the Karolinska Institute in Sweden.

This number of adipocytes (fat cells) seems to be achieved during teen years and then remains constant in life, even if bodyweight can and does vary a lot. The Swedish researchers tested subjects with high variation in bodyweight, and discovered little change in fat cell numbers.

It was already known that when our bodyweight increases, the adipocytes actually fill up with fat and expand in size but, until now, no one could say if their number experienced fluctuations or not. In this case, becoming slim again meant having to lose adipocytes.

The new study first looked at several hundred children, adolescents and adults of various ages, only to discover that adipocytes did indeed multiply through childhood; however, in adults, their number was stable.

Then the team studied the hypothesis that adipocytes could decrease in number in extreme circumstances, by sampling fat tissue from subjects before experiencing radical weight loss. Some subjects, for instance, were about to undergo "gastric banding", that shrinks the size of the stomach. When the patients had come to an end of their period of weight loss, their number of adipocytes was assessed again in samples of fat tissue. It appeared that the number of fat cells had remained the same despite the pounds dropped.

"It explains why it's so difficult to lose weight and to keep it off - those fat cells aren't going anywhere, and they're crying out for more," said lead researcher Dr Kirsty Spalding.

"It would be nice if we could find a way to lose fat by manipulating the numbers of fat cells, but there a lot of other options higher up the queue than that - such as diet and exercise. The real benefit of this is that it gives us solid evidence that we can use in future research into obesity and its causes," Dr Paul Trayhurn, from the University of Liverpool, told BBC News.

Despite all that, not everybody is convinced by the results of this research.

"We know that, sitting in adult fat tissue, are lots of cells that don't contain fat, but are capable of doing so if the nutritional conditions are right. They can almost certainly do so without dividing and therefore would not be 'counted' using this technique. I think it is premature to conclude that, by the time we are adolescents, the 'game is up' in terms of the number of fat cells we can possess," Professor Stephen O'Rahilly, from Cambridge University, told BBC News.