When it comes to the children of Lazy Town Sportacus makes quite a big deal out of the concept of being healthy. Teaching them the importance of being fit all while teaching the kids valuable life lessons(almost like he's their father figure). In fact, he's like that to everyone in LazyTown(only less of a father figure and more as a dutiful hero). The only exception to this is Robbie. Robbie's the only person in LazyTown that Sportacus doesn't talk about health with. He never really tries with him. It's not because he doesn't care, its actually because of a few reasons.
One: Robbie has exceptional healing abilities so it doesn't really matter what he eats, and two: He is one of the most active people in LazyTown (weather he likes it or not), so exercise isn't really an issue, and three: He's too damn stubborn to take his advice anyway!
Robbie is, in fact, half elf, so he has an their natural ability to heal himself at a far greater rate than a human. An elf's healing ability can be 5-10x greater than any normal human's, so sugar would do little to no damage to Robbie's body, as he already has an unusually high healing factor than most half elves.
Although Robbie will deny it up and down, he is one of the most active people in LazyTown. (When he's not sleeping of course.) He spends most of his time thinking of ways to rid himself of Sportacus and when he does come up with a plan to get rid of Sportacus, he puts all he has into it mentally, emotionally and, most importantly, physically. he also does other things like invent, pace his lair, dance around like an idiot, and even sing which all require a good amount of physical effort.
And finally, well, hes just really stubborn! That's just how he is, and Sportacus loves him for it anyway...
