She is known for her unconventional choices and now US first lady Michelle Obama is setting another precedent by the first presidential wife to appear on a reality TV series.

The First Lady will make a guest appearance on the popular series 'Iron Chef America' which features British cook Nigella Lawson as a judge, reported Daily Mail online.

The episode of the popular series, which pits well-known chefs against each others, has been filmed at the White House and will be aired in the New Year.

Many of the ingredients for the meals prepared in the show were chosen from the recently planted White House vegetable garden.

Michelle agreed to take part in the show to promote her campaign of healthy living. During the show, which attracts an audience of 1.5m in the US, she will be seen talking to the chefs about the importance of getting children to eat vegetables.

It is the first time a First Lady, or even a member of the White House staff, has featured in a TV reality show.

The move is likely to open up the White House to more criticism over its increasing links to Hollywood.

Last week it was revealed that a list of visitors to the White House in the first nine months of the Obama presidency was peppered with celebrities, including Oprah Winfrey, George Clooney, Brad Pitt and Denzel Washington.