What causes belly fat in young adults

nutrition : The number of fat cells remains constant in adulthood

A new study found that the number of fat cells in the body remains constant throughout adult life. The discovery suggests that the process of weight gain in children and adults is fundamentally different.

In adults, weight gain or loss is associated with a change in the size of the fat cells - also called adipocytes - that build fat deposits in the body. Children, on the other hand, can gain fat by increasing the total number of fat cells in their body.

That could mean people who get fat during childhood have a harder time losing weight later in life compared to people who put on pounds during adulthood, says Kirsty Spalding of the Karolinska Institute in Stockholm, who led the new research .

Although the number of fat cells remains constant in adult life, Spalding and her team found that the same cells are not permanent. It is a dynamic process of cell death and newly emerging cells.

Constant number

Spalding and her team took abdominal fat biopsies from 687 people, both lean and overweight, and recorded the number and size of the fat cells, as well as age, gender and body mass index. In combination with previously collected data from children, they showed that the average number of fat cells increases from around the age of 20, then remains relatively constant and is closely associated with the body mass index.

The researchers also looked at 20 obese people who were undergoing gastric-shrinking surgery to reduce food intake. When Spalding and her team examined these volunteers again two years after the procedure, they found no reduction in the number of fat cells: the subjects still had more than 80 trillion body fat cells, the team calculated, although they had lost an average of 18% of their weight. Rather, the volume of the individual fat cells was reduced, not the number, reports the team in Nature (1).

Nevertheless, fat cells continuously die off and are replaced by new ones, even in adults, according to Spalding and her team. They found this out by studying fat obtained from liposuction of 35 people who lived between 1955 and 63 during the Cold War nuclear test when the atmosphere was slightly more radioactive than normal. Food that was grown and consumed during this period had elevated levels of an isotope called carbon-14.

Fewer cells are aware of increased carbon-14 values ​​than would have been expected if the cells had not renewed, the team reports.

Lose weight

If cell biologists can find out how exactly this cell renewal is regulated, it could become possible to develop drugs that intervene in this process - which could potentially help to prevent weight loss once it has been lost.

Spalding says such a drug would be best given to patients who have been through serious weight loss therapy, such as stomach surgery. "You have to be very careful with that," she warns.

"It would be very dangerous to give such a drug to patients while they are overweight," added Spalding. Reducing the fat cells while the person still has a lot of fat would put extra stress on the remaining fat cells, which could lead to metabolic complications such as diabetes, she explains.

"Just take a pill, lose weight, problem solved - it won't be that easy, I think," she adds.

Perhaps more important is the confirmation that fat cells can proliferate in childhood, but not in adulthood, says Spalding. The underlying factors may be both genetic and dietary.

So although obesity seems to run in the family, having a normal weight at a young age will help maintain healthy fat cell counts in adulthood. "People with children should make sure that they have a healthy lifestyle - that is the message that can be drawn from this," says Spalding.

(1) Spalding, K. L. et al. Nature advanced online publication, doi: 10.1038 / nature06902 (2008).

This article was first published on May 5th, 2008 at [email protected] doi: 10.1038 / news.2008.800. Translation: Sonja Hinte. © 2007, Macmillan Publishers Ltd

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