AceShowbiz - Britney Spears' diet is so clean she's sick for days every time she eats a steak.
The Toxic singer is in full work-out mode for her upcoming Piece of Me Tour in North America and Europe and she admits she has to watch what she eats, so as not to get ill.
"When I'm in work mode, I want (to eat) very clean," she tells Entertainment Tonight. "I want clean chicken and veggies, that's it. My stomach is so sensitive, if I have a steak, I will be sick for three days.
"A burger is fine, but I have the small burgers from McDonald's. The Happy Meal!".
Britney is about to embark on the ultimate work-out - 30 shows in 51 days.
"This round of shows that we are doing on tour, they are back to back, so each show is like... I don't have time apart, besides flying. My show is a work-out in itself. It really keeps you strong".
And Sean Preston and Jayden James, her sons from her marriage to Kevin Federline, will be joining mum on the road.
Spears reveals the boys will be helping her finetune the set list each night: "My kids, they have been putting new remixes into my show and stuff...," she tells ET. "There is one of the new songs on the radio, and (my son is) like, 'Mom, that is so cool!' So I'm putting all these different new songs in my show".
The Piece of Me Tour kicks off on 12 July at Maryland's MGM National Harbor.