I eat a sugar rich diet and have a very strong body & immune system, until I started eating meat more than usual and I started getting ill more.
Also I eat a lot of cheese and eggs also, so protein was never an issue but eating the likes of steaks and very fatty patty burgers I have felt the difference.
Sugar is not as bad as made to believe, it is if you are never active, luckily I have a pretty intense job, muscles need glucoze.
I gain muscle and strength better on this diet.
I do eat balanced.
I eat veg.
I eat fish.
I eat nuts.
I eat pasta / rice.
I eat anything just that I have a higher preference for the aforementioned and have witnessed changes in eating way more meat than usual.
It's different for everyone.