[jlaporte]

Treating protein as calories is a category error.

Fat and carbs are energy, properly treated as calories. Protein is not (in a non-starving person) used for energy, and it should be measured in grams not calories. The input calories weren't lost, they were converted to protein for use building body structure instead of energetic use.

If the authors wanted to make an honest argument here, they would show the relative conversion of feed calories to animal protein across different livestock.

[enoint]

I think the authors are sincere; the original title is "Only half of the calories produced on croplands are available as food for human consumption". The commenters here are talking about beef, with very little reflection on 16% of our farmed calories devoted to biofuels.