When Mrs Obama first stepped on to the international stage, her arms made almost as many headlines as her husband's policies.

How does a woman of 45, an age at which most ladies banish sleeveless items to the furthest recesses of the wardrobe, maintain triceps that would not look out of place on an Olympic athlete?

The beans were spilt by Cornell McClellan, Mrs Obama's long-time personal trainer. She began exercising at his Chicago fitness studio in 1997 and he estimates that she has notched up 1,872 workouts since then. Most of these sessions were conducted at 5.30am, as the exercise-loving Obamas are famously early risers.

"She's truly committed herself to the importance of health and fitness," Mr McClellan said.

The "utimate arm-shaping superset" is a mix of tricep pushdowns, using a pulley as resistance, and hammer curls done while holding a pair of dumbbells. Two or three sets of 15 repetitions are enough to banish 'bingo wings' and give the arms definition, according to Mr McClellan. Do them and you too could be carrying off a sleeveless shift and pearls, as Mrs Obama did in her official White House portrait.

The arm exercises come at the end of a punishing workout routine for Mrs Obama which also involves weight training, rope-jumping and kickboxing.

Details of her fitness plan were featured in the October issue of US magazine Women's Health, accompanying an interview in which Mrs Obama discussed her attitude to food and fitness.

"I do love a good burger and fries. French fries are my favourite food in the whole world. If I could, I'd eat them at every meal - but I can't," she said. "My whole thing is moderation. If I make good, healthy choices most of the time, then having what I love every once in a while won't hurt. I have to exercise and eat in a balanced way. If I start ignoring both, I will put on weight.

"For me, getting enough sleep, eating right and exercising reduce my stress levels. And a really good workout is a great stress buster."

Mrs Obama said her toned figure did not come naturally. "I am fortunate in that I'm 5' 11', so it takes a while for the weight to be seen, but it'll come. If I didn't exercise and eat right I would be heavier, and I have been."

The Obamas have instilled the healthy living ethos in their daughters Malia, 11, and Sasha, eight. Mrs Obama explained: "I'm the mom, so I monitor - I am with the kids every single meal. But Dad is no slouch either. He doesn't believe that the kids should have dessert every single night; that should be a weekend treat."

(Agencies)