About 90% of energy is lost from one trophic level to the next
People need to take up protein. If the protein comes with significantly more calories than they burn, they're more likely to gain weight.
Maybe because it can be read as if I were arguing in favor of eating more meat.
I am not. I am just pointing out why primitive advice such as "Just replace the meat in your diet with grain" might lead to new problems.
People should stop reducing this discussion to the matter of calories.
As far as I know people who eat too little protein, overeat on stuff like grains for this very reason. The body wants the protein.