Santorio Santorio – physician, physiologist, and weight-watcher

Sue Reeves, PhD, RNutr
University of Roehampton, London, UK


Figure 1. Santorio’s static weighing chair
Courtesy of the Hagströmer Medico Historical Library
Karolinska Institutet, Sweden

Santorio Santorio (1561-1636), also known as Sanctorius, has been described as one of the founding fathers of metabolic balance studies and was influential in bringing the methods and experimental protocols of mathematics and physics to medicine.1 His introduction of precision instruments for quantitative research into the medical sciences helped lay the foundations of modern medicine.

Educated in Capodistria and then Venice, Santorio went to medical school in Padua at the age of fourteen. In 1582, at the age of twenty-one, he was awarded his medical degree. He practiced medicine in Italy, Croatia, Hungary, and possibly Poland (there are unconfirmed reports that he was summoned to treat the King of Poland). In 1614 he accepted the chair of Medical Theory at the University of Padua, while at the same time continuing to practice, notably with the Venetian aristocracy.

During this time Santorio invented many instruments, among these the wind gauge and the water current meter, but he mainly focused on apparatus that could be used in medicine such as a device to measure pulse rate known as the pulsilogium and on a tool to remove bladder stones. He is also credited along with Galileo, with whom he was an associate, to have invented the thermoscope, and in particular to have added the numerical scale; this instrument evolved into what we now call the thermometer.2 However, the invention that Santorio is mostly commonly associated with is the static weighing chair (Figure 1). This was a self-built contraption using a balance beam mechanism that comprised of a chair on a platform that was suspended from the ceiling with a large Roman steelyard that enabled Santorio to monitor his bodyweight. In fact, Santorio spent much of his time in this static chair measuring his own weight before and after eating and drinking, while working and sleeping, after evacuating his bladder and bowels, and purportedly after sex, diligently measuring daily changes in body weight. He often deprived himself of food so he could measure the effect on the weighing chair. He recorded data over a period of more than thirty years, and consequently this has been described as the first documented research into human metabolism. Although the raw data has not been kept, he did publish his findings in 1614 in ‘Ars de static medicina’ (the art of static medicine). This volume has since been reprinted many times and in several languages.

In the course of his research into changing body weights Santorio noticed that the amount of visible body eliminations were much smaller than the volume of material consumed as food and drink. He concluded that the difference must be lost through the skin or through the mouth during respiration, and he labelled this ‘insensible perspiration’.3 He established that insensible perspiration was not a constant but would fluctuate depending on internal and external factors such as fever, cold, sleep and nourishment. He believed food and drink were vital to the production of insensible perspiration and therefore observations of insensible perspiration were key to maintaining good health. His work not only emphasised the link between food and well-being but emphasised the importance of bodily evacuations, since ultimately health was an outcome of the balance between ingestion and excretion. He theorised that the amount being consumed should be proportional to the amount of liquid being perspired by the body to ensure good physical condition and the absence of disease. As well as monitoring body weight changes, the weighing chair could also be used to regulate dietary intakes since the machine not only measured what was being consumed but could be used to ensure the person remained a set weight i.e. in energy balance. Some accounts of the weighing chair reported that when adequate amounts of food and drink had been consumed the chair dropped down in response to the increased body mass, thus putting the table out of reach, compelling the person to cease eating.4,5 Although Santorio used his weighing chair principally for his own copious measurements and experiments, he also used the device to evaluate and monitor his patients too.

As well as the prominent tome ‘Ars de static medicina’, Santorio wrote several other notable publications, including: ‘Methodus vitandorium errorum omnium qui in arte medica contingent’ (methods for avoiding errors that occur in the art of medicine) that was published in 1602 and was intellectually highly regarded by other physicians, in which as well as reporting his own experimental observations he referred to and discussed the work of Hippocrates, Galen and Avicenna. The ‘Commentaria in Primam Fen primi libri Canonis Avicennae’ (a commentary on the first book of Avicenna the Canon of Medicine) was published in 1624 and provided details of the instruments Santorio had invented for physiological experiments and medical use including the thermoscope.

Eventually Santorio left his teaching post at the University of Padua to spend more time with patients and his research. He was made president of the Venetian College of Physicians in 1630, the same year in which he was asked by the Venetian government to lead the efforts against the plague and act as head of public health for the City of Venice. Santorio died on 22 February 1636 at the age of 75 from a urinary tract infection, and was buried in Venice in what was the Church of the Servi.6

Throughout his medical career Santorio was instrumental in introducing the methods and experimental protocols of mathematics and physics into medicine. His use of medical instruments and quantitative measurements helped lay the foundations of modern medicine but also made him the founding father of metabolic studies and the first documented weight-watcher in the history of science.



  1. Eknoyan, G. Santorio Sanctorius (1561-1636) – Founding father of metabolic balance studies. American Journal of Nephrology 1999: 19, 233.
  2. Mulcahy, R. Medical Technology: Inventing the Instruments. The Oliver Press; 1997: 21-24.
  3. University of Virginia. Vaulted Treasures. Accessed 26.1.15.
  4. Dacome, L. Balancing acts: picturing perspiration in the long eighteenth century. Studies in History and Philosophy of Biological and Biomedical Sciences 2012: 43, 379-391.
  5. Regis, E. Investigating the nature of life in the age of synthetic biology. Oxford University Press: 2009.
  6. Magill, F.N. The 17th and 18th Centuries: Dictionary of World Biography, Volume 4, Routledge, 2003: 1209-1211.


SUE REEVES, PhD, RNutr is a principal lecturer, registered nutritionist, researcher and program convenor for Nutrition and Health at the University of Roehampton, London.