Just measuring your waist size doesn’t tell you as much about your blood sugar and cholesterol levels as an ultrasound scan of your belly fat does — even when you already know someone’s weight and age.

Measuring belly fat with an ultrasound shows a stronger link to bad blood sugar, cholesterol, and fat levels than just measuring waist size, even when you account for a person’s age, sex, and overall weight.

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.

Middle-aged men who gain 14.6 cm or more around their waist have 1.7 times the risk of diabetes, even when their overall weight change is considered. This finding is from the abstract summary - full study details were not available

Men with metabolic syndrome who also have a waist size of 94 cm or larger have a 30% chance of silent heart disease, compared to 20% for those without large waists, according to the study. This finding is from the abstract summary - full study details were not available