Almost 3 out of 10 middle-aged people have mismatched fat distribution: some have more internal fat but less under the skin, while others have the opposite, showing fat isn't always stored the same way.

In a group of middle-aged people, about 3 out of 10 women and men have too much fat under the skin of the belly, while about 4 out of 10 have too much fat around their internal organs, based on CT scans.

As people get older, they tend to have more fat around their organs and less under the skin, making weight and waist measurements less reliable for detecting health risks in seniors.

People with less fat under the skin but more fat around organs have more metabolic problems than those with more subcutaneous fat but less visceral fat, even if they weigh less and have smaller waists.

Even among people classified as obese by BMI, about 1 in 4 men and 1 in 10 women don't have excess fat around their organs, showing BMI doesn't always reflect internal fat levels.

Even people with a large waist size can have normal levels of internal fat: about 1 in 3 men and women in this study had this, showing waist size isn't always a perfect indicator of visceral fat.