Santorio Sanctorius was an Italian physician and scientist who conducted the first quantitative balance studies in human nutrition. Repeatedly over a 30-year period, Sanctorius would sit on a large scale and weigh all the food and drink he consumed and all the feces and urine he excreted and calculate the difference as insensible perspiration.
“If eight pounds of meat and drink are taken in one day, the quantity that usually goes off by insensible perspiration in that time, is five pounds,” he wrote in his Ars de Statica Medicina published in 1614. The book went through 28 editions and was popular well into the late 1700s.
Sanctorius was a prominent physician and medical consultant in great demand. He never married and dedicated all his time to his work. In addition, he invented several medical instruments, including a forerunner of the thermometer. He is considered the founder of the study of modern metabolism
Sanctorius died at 75 from complications of a urinary tract disease.