Beyonce Knowles buys clothes which are too small for her as a motivation to lose weight.

The singer-and-actress, who is famed for her curvy figure, admits it takes a lot of hard work for her to stay in shape so she needs to have a goal.

She said: "I buy something too small and then say, 'I have a reason.' I need to wear these jeans or this hot dress."

The 27-year-old beauty also says her dream of winning an Oscar drives her on when she is working out.

Talking about a painting in her gym which features the famous gold statue, she revealed: "I look at it, and I'm like, 'OK, I have to stay in shape.' "

Although she would like to lose a few pounds, Beyonce - who is married to hip-hop star Jay-Z - admits she wasn't happy when she shed 15lbs to play Deena Jones in 'Dreamgirls'.

She added to Self magazine: "I felt very chic, like a model. But it didn't look natural for me. I didn't feel very sexy or feminine, and I didn't have much confidence because I didn't feel like myself."