Why is it that when men gain weight, they tend to develop potbellies?

The answer has to do with how the body stores fat. When men gain weight, the default storage place is the belly. Think of it like the trunk of a car, said Dr. Zhaoping Li, director of the Center for Human Nutrition at the University of California, Los Angeles.

Just like people loading up a trunk for a picnic at the park, “you can put things there; no problem,” Li told Live Science. 

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But if men eat too much and don’t get enough exercise, then just like a jam-packed trunk, that belly space is going to run out of room, Li said. Once a man has a full potbelly, the body starts storing fat elsewhere, which is extremely unhealthy, she said.

“When they run out of storage place in the belly, that’s the time the fat starts to accumulate in the liver, pancreas and muscles,” Li said. “Then, you start having real medical issues like [type 2] diabetes, high blood pressure, high cholesterol and heart disease.”

In contrast, because of estrogen, women tend to store fat in their hips and legs, especially their thighs, Li said. Fat in these storage areas can give women needed energy when they are pregnant or breast-feeding, Li said.

“Women genetically have more capacity to store fat [than men do],” Li said. “That is part of our survival.”

What’s more, storing fat in the hips and legs isn’t associated with the same health problems as belly fat, Li said. However, if a woman’s fat-storage areas in the hips and legs fill up, then she, too, can develop a stomach paunch. If that paunch fills up, then the body will start storing fat elsewhere, putting the woman at risk for the medical problems associated with a full potbelly, Li said.

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