03/03/2008 AT 02:20 PM EST
's secret for her unusually good looks: the usual, diet and exercise.
"I have egg whites and pineapple for breakfast with hot water and lemon," the Barbados beauty, 20, tells the News of the World
magazine. "For lunch I have fish and potatoes. I hate vegetables, but I make myself eat them. For dinner I have fish again."
While her body fluctuates between size 2 and 4, she says she is extremely proud of her booty. "I keep working at it as I want it to be perfect," she says. "It makes my clothes look good – and guys like it!"
Having been named to PEOPLE's Most Beautiful People of 2007
list, the singer, who claims she's 133 lbs. and 5'8", says she maintains her enviable physique by exercising with a personal trainer who helps her in her quest for the perfect body.
Having been recently linked to Chris Brown (with whom she was snapped in a Jamaica swimming pool
), Rihanna says of her personal life: "I'm single. If a good guy came along we'll make it work, but for now I'm having fun being a single woman."