Protein consumption is staying constant, because concentration has dropped, and people eat more total food to bring total protein back up. Acc to the article.
Which is a win/win for industrial food. The article says industry is incented to replace protein with cheaper fat and sugar. So a volume of food sold costs less to produce. And then people turn around and eat/buy even more, to make up for the lower protein concentration.
People are eating more, hence the 8% increase in carb/fat consumption. But since they are actually getting a hair less protein it means people must be eating food with less protein in it on average.
The interesting part seems to be the increase in carbs/fats at 8% over the same 35 years.