Medical student's apparent celiac disease responded to giardiasis treatment

> No matter how much he ate, he kept losing weight. At one point, he logged his caloric intake for a college nutrition class and found that he had been eating seven thousand calories a day, despite looking sickly thin

Is this even possible? And- only half joking- if it is indeed possible, why isn't there a queue of people waiting to get the parasite installed in their body?

I think there are people that have intentionally swallowed some tapeworm eggs for a similar reason to this.