NEW SCIENTIST A team of Swedish researchers has found that humans determine their total number of fat cells in childhood. New cells spring up and old ones perish, but their numbers change little after adolescence. By measuring radiation absorbed after nuclear bomb tests in the 1950s and 60s, researchers found that our fat cells quickly regenerate.
But obese people turn over far more fat cells than others, says Kirsty Spalding, a biologist at the Karolinska Institute in Stockholm. The difference could explain why people battle to keep weight off after a diet.
"The take-home message is be careful what you feed your child," Spalding says. "Do everything you can to make sure you don't blow out your fat cell number when you are young." . . .
We recycle about 10% of our fat cells each year, and every 8 years, half our adipocytes have been replaced.
But Spaulding did find that young obese people add twice as many fat cells each year as others, on average. "This could be part of the reason it's so hard to keep weight off," Spaulding says.
After plugging those numbers into a mathematical model, her team found that obese people start building up their fat cells much faster and at a younger age – about two years old – than thin people.