In women with belly fat, waist size and total body fat are linked to both deep belly fat and under-skin fat.

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.

For women with belly fat, certain blood chemicals like insulin and specific fats are linked to the amount of fat stored deep in the abdomen.

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 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.

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.