"There are special receptors on the fat cells deep inside the abdomen which are specifically intended to hook up with stress hormone -- and stress hormone stimulates them to accept fat, " said Peeke, a former senior scientist at the National Institutes of Health.

CNN: Health - Stress is bad, but one expert says it's also fattening

Even with a healthy BMI, for example, such people may harbor a lot of visceral fat, deep in their abdomen, a type of fat that is particularly dangerous to health, since it secretes hormones and substances that can hamper insulin's ability to break down sugar.

CNN: Obesity paradox: Why being thin with diabetes is dangerous