Professor of physiology at the University of Glasgow; Born April 23, 1923; Died August 23, 2007. JOHN Durnin, who has died aged 84, was an international authority on the energy expended in a wide range of human activities and a book he co-authored is still the reference standard.

He and his small team made meticulous measurements on people engaged in various forms of work, leisure and household activities. Some of these measurements were made on workers themselves (eg miners, bricklayers, lumberjacks), but others were carried out on volunteers. Either way Durnin was usually able to combine his work with pleasure. Sometimes it was of great practical value to himself and family: eg persuading students to have their energy expenditure levels measured in his garden and house while digging, hoeing and sawing trees.

Durnin was also known internationally for his work on the measurement of obesity and weight reduction. He demonstrated the pitfalls of using height and weight measurements as an indicator of obesity, and promoted the use of skinfold callipers as a more accurate measure. He compiled tables for the calculation of body fat from skinfold measurements, and these are still widely used.

This work involved measuring the body fat of more than 1000 individuals of a variety of builds and types by weighing them under water and then measuring their skinfolds at a number of sites.

The underwater weighing also often had its interesting aspects, and we met a number of interesting and even famous individuals in this way: Edwin Morgan for example, and Antoinette Sibley, Anthony Dowell, David Wall and Margot Fonteyn.

He also was able to show that Fonteyn (then in her sixties) was able to push her heart rate up to almost 190 per minute - only slightly less than young fit adults are able to do - because of her having maintained her fitness level so high throughout her life.

Durnin, a father of six whose wife, Joan, predeceased him, was a handsome man whose often lugubrious expression disguised the kick that he got from life. Nothing appeared to faze him. He was able to assimilate new material to include in a lecture right up to the time of delivery, and would arrive for work some 20 minutes before his lecture was due to start with words such as "what do you know about the liver?"

Many other things could be said about Durnin: his expertise at squash and skiing, his studies on roughage and digestibility, his enthusiasm for travel and the good life. He was not afraid to be different.

Before beginning a paper at a conference in Nice one hot and sunny afternoon, he announced - to much applause - that he would not show the slides he had brought, but if the blinds could be drawn aside and the windows opened he would simply talk to the audience.

He demanded high standards from others. On a trip to give a paper in London we breakfasted at Euston Station and he made at least six complaints about various aspects of the environment, food and service. On suggesting that maybe he could let it go at that, he replied: "If it wasn't for people like me, b*****s like you wouldn't get a decent service anywhere". In these days of assessments, appraisals and conformity, we're unlikely to see his like again.