Fancy a mint, Britney Spears? From what we've heard, our girl Britney suffers from such bad breath, that a source close to the star says it "absolutely reeks." Not. Even. Nice!

What's the culprit behind her bad breath? It's looking more and more like Spears' new 600 calorie-a-day diet! “Every day she eats four egg whites for breakfast, a few hours later she has a whey protein shake made with water and a couple of strawberries," said a source. "Lunch is a half a steamed chicken breast and a salad, then another shake, and for dinner more lean meat with veg­gies. It’s barely 600 calories a day.”

Of course, the reason that our girl is on such a strict diet is so that she can look her absolute best while judging on 'X Factor' -- she must be expecting serious critiques on her own critiquing abilities once the show airs -- and the diet is having quite the effect on her breath.

“It must be the acids in her tummy or something from this cra­zy diet she’s on because her breath will start smelling 20 minutes after she brushes her teeth," said a source.

But bad breath aside, it looks to us like her diet is working, because Spears posted a cute picture of herself in her house, rocking some new glasses and a bikini, and she looks soooo good! "Having some fun in the sun... don't want summer to be over!" she tweeted.

Watch the Britney Spears 'Til the World Ends' Video