There are perhaps some things worth considering, much of it in wild opposition to other studies, but I’m going to say that this type of prognostication without myriad examples of success in application is probably dangerous to be considered as expert advice to the average disinterested person.

If you are interested in an example of a healthy person that eats this way, check out durianrider on YouTube. Dude lives on a bicycle though. It is actually hard to get fat on just sugar, because such a small amount produced satiety so quickly - unless you also wary regular foods like starch and fat along with it, and then you are going to explode.

So I’d say that he’s not wrong, it’s just not practical for most people. Honestly, if you’re fat, and I once was, the easiest and most reliable way to lose weight is to cut out all fats. You’ll be amazed how much that reduces total calories without affecting the way you feel.