(BANG) -Lady Gaga has switched to a gluten free diet.

The 'Poker Face' singer has started the next leg of her huge 'Born This Way Ball' tour in Sofia, Bulgaria, and she has opted to go on a new diet to make sure she is in the best shape for the gruelling workout.

A source said: ''Gaga has decided to go on a major body blitz and cut out all gluten and wheat from her diet, which is very hard to do. She has given her people strict instruction to advise staff at venues and restaurants about her new diet because she is taking it very seriously.

''Her aim is to drop 10lb in a month.''

The 26-year-old singer is thought to be rationing her carbohydrate intake to just two portions a week, and living off a diet mainly consisting of fish, chicken and vegetables.

The source added: ''She allows herself one potato or rice portion a week and has been snacking on Ginnybake cakes from wholefood shops - they are gluten free cookies.''