“Approximately 3,200 kcal could meet the daily energy requirements for physical exercise for a 70 kg person whereas 2,600 calories was sufficient for simple office work.

The metabolism of a farm worker during harvesting would require 4,300 kcal. The peak values of the daily calorie consumption for lumberjacks would amount to approximately 6,000 kcal for a 70 kg person. Long-distance racing cyclists, however, could reach a peak daily metabolic rate of 11,000 kcal.

Rubner [see Roux, 1895] believed that the limiting factor for the uptake of calories in the human body was the intestinal system. A repeat of such great exertion over several days would inevitably lead to loss of body weight.” (Tipton, 2014, p.62).

Reference

Roux, W. (1895) Collected Texts about the Development of Organism. Volume 1: Functional Adaptation [in German]. Leipzig: Engelmann.

Tipton, C.M. (Ed) (2014) History of Exercise Physiology. Leeds: Human Kinetics.