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.

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.

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.

Among people with a normal weight (BMI under 30), about 1 in 10 men and 1 in 9 women have too much fat around their internal organs, showing that weight alone doesn't always reveal hidden health risks.

Even people with a normal waist size can have too much fat around their organs: about 1 in 4 men and 1 in 12 women in this study had this hidden fat, showing waist size alone isn't always reliable.

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.