The number of fat cells you have remains fairly constant throughout your life, regardless of whether or not you diet, or are thin or fat, say researchers at the Karolinska Institute, Sweden. In a study published in Nature they have demonstrated that we continually create new fat cells to replace those that are breaking down. The scientists have also demonstrated that fat people do this at a faster rate than lean people – people with obesity’s fat cells die at a faster rate and are created at an equally faster rate.

It has been generally believed that adult humans cannot create new fat cells. We have thought, until now, that fat cells only and simply increase their fat mass by adding more lipids into fat cells that already exist in order to settle their body weight – this is true, but that is not the end of the story. Research lead by Kirsty Spalding, Jonas Frisén and Peter Arner has recently shown that adult humans constantly produce new fat cells regardless of their body weight status, sex or age.

Peter Arner, Professor, Department of Medicine, Huddinge, said “The total number of fat cells in the body is stable overtime, because the making of new fat cells is counterbalanced by an equally rapid break down of the already existing fat cells due to cell death.”

The study used a combination of two unique procedures:

1. The scientists were able to determine the age of fat cells in the body by measuring the incorporation of radioactivity from the atmosphere into the DNA of the fat cells.

2. They compared the mass of the fat cells in relation to the full amount of adipose tissue in a extremely large number of human subjects whose body weights varied widely.

The scientists found that people who have obesity produce approximately twice as many new fat cells annually as lean people. They also found that fat cell death is happens at twice the rate among people who have obesity, compared to lean people. Even if the people with obesity they studied lost a significant amount of weight, their total number of fat cells in the body remained constant, but the size of individual fat cells fell substantially.

The scientists say the findings of this study could provide a new target for the treatment of obesity. If we can attack the signals and genes in fat cells and control the formation of new such cells we may be able to treat obesity more effective.

Peter Arner said “The results may, at least in part, explain why it is so difficult to maintain the weight after slimming. The new fat cells generated during and after weight reduction need to fill up their lipids rapidly.”

“Dynamics of fat cell turnover in humans.”
Kirsty L. Spalding, Erik Arner, Pål O. Westermark, Samuel Bernard, Bruce A. Buchholz, Olaf Bergmann, Lennart Blomqvist, Johan Hoffstedt, Erik Erik Näslund, Tom Britton, Hernan Concha5, Moustapha Hassan, Mikael Rydén, Jonas Frisén & Peter Arner
Nature AOP, doi:10.1038/nature06902 (2008).

Karolinska Institutet

Written by – Christian Nordqvist