Jan Dequeker -- professor emeritus at Catholic University at Leuven in Belgium and rheumatology lecturer at Italy's University of Lovinio -- said the woman suffered from hyperlipemia, a condition caused by overeating and lack of exercise, the Italian news agency ANSA reported Wednesday.
Dequeker, an art buff, said he found evidence of the disease when he examined "Mona Lisa," whose countenance has bewitched at lovers for centuries.
"There is a swelling on her left hand which shows a buildup of subcutaneous lipids, as does the puffiness around her left eye," Dequeker told ANSA.
Dequeker said the typical age for the disease's onset in women -- 30-to-35 -- is the span when experts believed the model posed.
The theory isn't the first advanced by medical experts-art lovers.
One group of medical researchers said the model's mouth is closed because she was undergoing mercury treatment for syphilis, turning her teeth black. An American dentist claimed the expression was typical of people who have lost their front teeth.
A Danish doctor posited she suffered from congenital palsy.