When I tried to find a recommendation for sugar I mostly found "added sugar should be no more than 5% of your calories". Eg https://www.jamieoliver.com/news-and-features/features/how-m...

By keeping his calorie intake the same but replacing all foods with those containing added sugar, he really tipped the scale. I suspect with more calories he might have gained some weight but would feel better and not have that liver issue.

I've never seen an honest documentary on nutrition.