Nutritionists salute Michelle Obama's burger

United States First Lady Michelle Obama, who has been pushing healthy eating with her national Let's Move campaign to fight childhood obesity, has copped a serve for visiting a takeaway where she ordered not only a hamburger, but chips and a chocolate milkshake.

The Washington Post reports the first lady stepped out of the role as Healthy Eater in Chief and into a storm of publicity by downing a hamburger the newly opened Shake Shack diner in Washington on Monday.

There she consumed a meal that equalled about 1500 calories or more, USA Today gasped - "the amount some women should eat for the entire day". The burger joint's website puts it at 1556 calories.

But nutritionists have since stepped in to defend Obama's actions and admonish the press.

"[This is an] unfortunate invasion of privacy for Mrs Obama," Alice Lichtenstein, professor of nutrition science and policy at Tufts School of Medicine in Boston, told ABC.

"She has kept her weight constant and engages in regular physical activity. An occasional indulgence is fine. For many people, that is what helps them keep on track most of the time."

ABC quotes other nutritionists as saying Obama's lunch was being unnecessarily scrutinised.

"While the goal for healthy eating is to limit choices like fries and shakes, occasional treats won't hurt. The problem is that many Americans do this more than occasionally," said Connie Diekman, director of university nutrition at Washington University in St. Louis.

"It is good to see that even someone as committed to health as the first lady knows that healthy eating is about balance, not perfection."

Meantime, even USA Today admits "Obama has been very upfront about her enjoyment of food and her own eating habits," adding she had told the news group in 2010 that she and her family try to eat healthy food most of the time, but that they are not "100 per cent perfect".

In fact, she admitted she loves "burgers and fries, and I don't want to live a life where I can never have them again. And if we told families and children that that was the answer, we'd never get there" with Let's Move.

- AAP