Non-obese people with a large waist circumference are at a higher risk of developing serious complications from non-alcoholic fatty liver disease (NAFLD) than obese people with NAFLD, according to a study presented at the 2016 International Liver Conference in Barcelona. The findings are the first of their kind to challenge current theories that NAFLD is directly linked to how obese an individual is, ScienceDaily reports.

NAFLD, a condition in which fat builds up in the liver, is present in up to 80 percent of obese people. The disease can cause inflammation of the liver and eventually lead to permanent liver scarring. However, Italian researchers believe “lean NAFLD" (present in 16 percent of individuals with a normal body weight) may be worse, leading to an increased risk of diabetes, high blood pressure and death.

For the study, scientists evaluated the features of the lean form of the disease in 323 diagnosed people with the condition, dividing them up according to BMI (body mass index, a ratio of weight and height), waist circumference and abdominal fat. They found a waist size greater than 35 inches for females and 40 inches for males, was significantly associated with a higher risk of metabolic issues, fat buildup and liver fibrosis compared with obese people with NAFLD.

The study suggests that the severity of NAFLD may not be necessarily linked to how obese a person is, but instead to the proportion of fat someone has along the midsection of his or her body.