As a child, Tarrare had a huge appetite and by his teens could eat a quarter of a bullock.For some years, Tarrare toured the country, stealing and begging for food. He would draw a crowd by eating corks, stones and live animals, and by swallowing an entire basketful of apples one after the other. In 1788, he moved to Paris to work as a street performer. Despite his unusual diet, Tarrare was slim and of average height. At the age of 17, he weighed only 45kg (100lb). When he had not eaten, his skin would hang so loosely that he could wrap the fold of skin from his abdomen around his waist. When full, his abdomen would distend. The skin of his cheeks was wrinkled and hung loosely. He is also known to have sweated heavily and had a foul body odour.
The cause of Tarrare’s behaviour is not known. While there are other documented cases of similar behaviour from the period, none of the subjects other than Tarrare were autopsied. Some speculated he suffered from hyperthyroidism, which induces an extreme appetite, rapid weight loss, profuse sweating, heat intolerance and fine hair. Others speculated that Tarrare had a damaged amygdala, as it is known these types of injuries in animals can induce polyphagia.