http://www.webmd.com/diet/20151109/belly-fat-is-bad-even-at-a-normal-weight?page=1
From their own website;
Normal weight women with extra belly fat had nearly a 50 percent increased risk of death during the study period versus a normal weight woman whose weight was more equally distributed throughout her body. Compared to obese women (measured by BMI only), the normal weight women with belly fat had a 32 percent higher risk of early death, the researchers found.
Dr. David Katz, director of the Yale University Prevention Research Center, in New Haven, Conn., and president of the American College of Lifestyle Medicine, said the study findings raise the question: who would have more belly fat and still be at a normal weight according to their BMI?
Some people are more prone to depositing excess fat around the middle, he said. This can lead to fat accumulation in vital organs, especially the liver, he explained.
Another group may be those who have excess body fat and illness, perhaps in early stages, causing loss of lean body mass, Katz said. Although it’s not clear from this study how many people might fall into this category, he added.
Regardless of why someone has gained weight around the middle, Katz said, “We have long known that all varieties of overweight are not created equal with regard to health risk, and that central obesity is the most concerning variety.”
In his editorial, Poirier wrote, “These new data provide evidence that clinicians should look beyond BMI. Although assessing for total fat mass with BMI to identify patients at greater cardiovascular risk is a good start, it is not sufficient.”