Katy Perry has admitted being on a diet "absolutely sucks".

The 'Firework' singer is currently on a strict eating regime in preparation for her 'Teenage Dreams Tour' but revealed she occasionally lets herself have "cheat days" where she allows herself a burger.

She told Rolling Stone magazine: "After this interview I'm going to have a nice healthy breakfast. I'm on a meal plan, which absolutely sucks - but on Sundays I get to have a cheat day where I go buck wild and eat In-N-Out Burger."

Katy, 26, also finds working out in preparation for the 95 date world tour especially difficult and said the rigorous dance rehearsals make her feel as if she is in training for the Olympics.

Describing her daily routine, she explained: "I'll work out, go to a vocal lesson, run through the entire set at rehearsals, go to dance rehearsal until 10:00 p.m. and then go home and sort through e-mails concerning the production. I feel like I'm training for the Olympics!"