Ever wonder if fat cells just get bigger or if you actually gain more fat cells when you overeat?

To find out, researchers at the Mayo Clinic fed 23 lean young men and women 400 to 1,200 extra calories a day by padding their diets with Snickers bars, milkshakes, and Boost Plus drinks.

After two months, the volunteers had gained about eight pounds. But that surplus got stashed in different depots. “Almost all the weight gain in abdominal body fat was an increase in fat cell size,” says Michael Jensen, director of the Obesity Specialty Council at the Mayo Clinic.

In contrast, “when people gained leg fat, they actually gained new fat cells.” Jensen’s earlier study estimated that when people gained 3½ pounds of new leg fat, they acquired roughly 2.6 billion new fat cells.

What happened when the volunteers tried to lose the weight

Next, Jensen had the participants spend two more months cutting calories and upping their exercise. The result: 6 of the 8 pounds disappeared.

“Everybody lost all or pretty much all of the abdominal subcutaneous or visceral fat they had gained,” says Jensen.

“The only fat that they hadn’t yet lost was some of the leg fat they had gained. So we concluded that it’s easier to shrink fat cells back down to their original size than to make fat cells go away.”

Are you stuck with those fat cells forever?

“We don’t know whether the new fat cells would have eventually gone away if people had kept off the weight long enough,” says Jensen. (Ironically, the leg fat that’s hardest to lose is also the least harmful to your health.)

And don’t assume that you’ll never gain new fat cells around your middle.

“If you gain enough weight, you have to make new fat cells,” says Jensen. “From an average small fat cell to the biggest of the big, it’s about a fourfold increase in size. They can only get so big.”

Photo: © Brent Hofacker/stock.adobe.com.