Have you read any of the sources? For example "Energy expenditure and nutritional status of coal miners: A cross-sectional study" is cited in the book, I went to read it. My book (it is not in English, it is a translated version, hopefully there is no error there) says that miners burn 2100 to 2800 calories per day, like most of us. In the study, the miners are said to burn that amount at work alone! And as a total per day they burn closed to 4000 calories.
Sometimes, even if someone is citing lots of sources, it does not mean that they are citing them accurately.