Researchers from Lawrence Livermore National Laboratory have found that the number of fat cells do not undergo any change during adulthood. The researchers used carbon dating for this study.
By applying carbon dating to DNA the scientists found that the number of fat cells remain constant throughout adult life in lean and obese individuals even after serious weight loss.
For the study the researchers used the pulse of radiocarbon to evaluate the fat cell turnover in humans.
Lead researcher Bruce Buchholz said that radiocarbon or carbon-14 is naturally produced by cosmic ray interactions with air and is present at low levels in the atmosphere and food.
He along with colleagues studied the uptake of carbon-14 in genomic DNA within fat cells to determine the dynamics of fat cell turnover.
The findings revealed that nearly 10 percent of fat cells renewed annually at all adult ages and levels of body mass index.
The study suggested that neither fat cell death nor its generation rate is altered in early onset obesity.
"Fat cells change in size but no one had ever measured fat cell turnover. An increase in cell size means it can hold more mass," Nature quoted Buchholz, as saying.
In the study, the team first looked at the biopsies of belly fat from 687 people, both lean and obese, and recorded the number and size of fat cells, as well as the subjects' age, sex and body mass index.
They also found that number of fat cells increases in childhood and adolescence, but levels off and remains constant in adulthood.
The team further looked at affect on number of fat cells even after drastic weight loss by radical reduction in caloric intake, such as through bariatric surgery.
The results showed that the treatment significantly reduced BMI and fat cell volume, however, it did not reduce the number of fat cells two years after the surgery.
"If you are overweight and you lose weight, you still have the capacity to store lipids because you still have the same number of fat cells. That may be why it's so hard to keep the weight off," said Buchholz.
The researchers believe that their findings would help in developing new therapies to manage obesity along with accompanying diseases such as high blood pressure and diabetes.
The study appears in online edition of the journal, Nature.