Michelle Obama dresses for practically

Michelle Obama is a practical dresser.

The US First Lady - famed for her stylish taste in fashion - says her decisions on what she wears are based on what she's doing that day because she needs to know she's in the right outfit.

She told blog Politico: "It's really just sort of, how cold is it? Do I have to stand outside, and what am I going to use to cover my arms if I'm freezing so I'm not shivering while I have to give a speech? It's really stuff like that. And I know people are sort of thinking that it's different, but it's real practical stuff like that."

In December, Michelle - wife of US President Barack Obama - stunned the fashion world by wearing a vintage dress to a high profile public event.

The mother-of-two wore a black lace outfit by the late designer Norman Norell to the Christmas in Washington concert and it is thought she was the only First Lady in history to ever wear a second hand gown for an official engagement.

Michelle bought the dress from New York Vintage and the boutique's co-owner Jon Schneck said: "We are truly honoured that the first lady has chosen a gown from New York Vintage as her first venture into vintage couture.

"Other dresses from our archive have been scheduled for use by the first lady later this year."

Michelle is a huge fashion fan and has previously praised it as vital saying: "Fashion is an American art form with ingenuity and craftsmanship that contribute so much to our economy and culture."