She may not be able to work out a Middle East peace settlement (just yet), but she can tell you how to lose those extra kilos and keep them off. Condoleezza Rice has gone the Jane Fonda route and decided to share her dogged commitment to fitness with the rest of the nation.

Washingtonians who were up early enough this week could have seen the secretary of state on the pre-dawn local news bulletins in a sky-blue T-shirt and black tracksuit bottoms, providing tips on how to stay in shape even when you spend much of your circling the world helping President Bush to spread democracy.

The 51-year-old diplomatic dynamo gets up at 4.30 every morning and never misses a session in the gym, wherever she is in the world. She works out for 45 minutes on a treadmill or an elliptical trainer (that awkward contraption with pedals and handles that you stomp, push or pull) and lifts weights three times a week. It is as simple and brutal as that.

She has some advantages. When in Washington, she uses the state department gym and its resident trainer, ex-marine Tommy Tomlo. In the course of three instalments of Fitness in the Fast Track aired on Washington's WRC-TV this week, Tomlo put her through her paces with a few minutes' warm up - spinning on a stationary bicycle - then worked on her core stability with some nasty-looking stomach crunches, and finally lifted hefty free weights on her shoulders. She did not flinch.

Weight does not appear to be much of an issue with the secretary of state, an unrepresentative representative of a country that is struggling with an obesity epidemic. But apparently she was once drawn to the dark side. Her one shock revelation was that she carried around some extra baggage in her last year at college.

She joined a sorority and began having communal meals and midnight snacks (her favourite was "pigs in a blanket", which in the South involves hot dogs and melted cheese stuffed into some dough). "Before I knew it I had gained almost 30lbs," she recalls.

However, as she rose in the academic world to become a star in foreign policy studies, she got a grip on her eating habits and has been far more careful ever since, even experimenting with the faddish end of the diet world.

"I ate low-carb for a while, low-fat for a while," she says. "But I find that what works for me is to eat a balanced meal." She shares the Bush family's aversion to green vegetables and admits having to force broccoli down.

That would seem to be a small feat for a woman who appears to wake up long before the rest of official Washington, even a good hour before her fellow fitness nut, George W Bush, with whom she first bonded seven years ago by talking sport. Like Rice, the president spends time in the gym every day, but his regime also takes him out to the fresh air. He ran obsessively in Texas and during his first term in office, but the strain on his knees has since converted him to the aerobic virtues of mountain biking. He now cycles on most of his trips and has had a couple of crashes, one in Scotland last July in which he lost control and veered into a police officer, who was hospitalised. Rice's gym-based routine runs less of a risk of diplomatic accidents.

The early starts, she warns, do not get less painful with time. It is just a question of willpower.

"When I get up at 4.30am I'm like anybody. I don't want to face the day. I think, 'Oh, I have to do this, I have to do that ...'" she confesses. "And after 40 to 45 minutes of exercising, I'm ready to go. So for me, it's not just physical, but mental, as well."

"I think I think better when I exercise," Rice says.

For any foreign secretaries aspiring to punch above their weight and go 15 rounds with Rice, she has some basic tips:

· If you are over 50, she recommends you "speed walk and walk hills instead of running". Power walking has less impact on the joints.

· Do not break your exercise pattern, even on the go. "Part of the secret of travelling well is to continue your routine when you're on the road," she said. "I absolutely schedule time to get up in the morning and exercise first."

· Do not give up. Rice tells Washington viewers about her father who had once been an athlete but gave up exercise and afterwards "encountered all kinds of health problems". She concludes: "It was a real lesson to me, and it said to me you have to exercise all your life."

The Condi fitness plan is not for the faint of heart. This is no everywoman. On top of her day job, she is also a concert pianist, a former competitive figure skater and enthusiastic tennis player. Do not try all of that at home, especially while mediating global conflict.

There is no doubt over Rice's value as a role model. If she can make time on her work schedule, perhaps anyone can. It is less clear what the secretary of state will get out of baring her biceps unless, of course, it is for the same reason politicians do anything.

She has claimed, insistently and repeatedly, that she has no interest in running for the presidency in 2008, and privately hints that she cannot wait to get back to the academic life in California. She says she cannot bear Washington. But that begs the question of why her press aides are thinking up such unconventional stunts to raise her profile. There is a "draft Condi" movement gathering steam, to make her the Republican presidential nominee. Putting forward a black woman who is "mildly pro-choice" on abortion may not suit the Republican right, but the party's tacticians see her as a potential vice-presidential candidate at least, the perfect foil to a Democratic challenge from Hillary Clinton. Clinton's exercise regime, unlike her husband's, is little-known.

As for what all this exertion will mean for the rest of us, the state department spokesman claimed, with a little deadpan menace, that it would make US diplomacy "muscular and agile". Is that a good thing?

But just how tough is it? Lucy Mangan tries out the secretary of state's workout

Condoleezza Rice has the use of private gymnasia wherever she goes, in which to practise her daily workout. I, alas, am limited to my local leisure centre. No spinning, I am told, outside official spinning-class hours. Pleas that my journalistic integrity depends on the bending of a few minor health-and-safety rules fall on deaf ears. So I adapt Condi's preferred two-minute warm-up to normal cycling on the exercise bike. Easy enough, although I suspect that if I were doing it at the US Secretary of State's usual hour of 4.30am instead of lunchtime, I would be weeping, and have to be carried from the room.

Next, she recommends 40 minutes on the cross-trainer. The copy of Grazia magazine I have brought to entertain me won't sit on the control panel, so the feeling of boredom is intense from the beginning. I don't know what Rice does to keep herself occupied - maybe she has action shots of Jack Straw addressing the European Parliament pinned up round the room - but 25 minutes in, my attempts to penetrate the mysteries of the most powerful female political mind in the world are halted by the pain in my thighs. At 29 minutes and 43 of the longest seconds in the free world, I have to stop.

There's a momentary embarrassment when my legs give way as I walk to the mats, but I channel the spirit of Dr Rice, a woman rarely deflected from her goal - be it completing a set of core-strengthening reps or convincing a populace that invading a country less threatening than Belgium makes sense (and will again!). I embark on my abdominal crunches. Fifty-two of those and a series of what should probably be described as best endeavours with an exercise ball and I am fit to drop.

Condi's "power-walking" is, of physical necessity, modified to "doing everything in my power to walk home", but at the halfway point I collapse in Starbucks. If I had the strength, I'd raise my grande in tribute to an Americano who, beneath the black trouser suit, must be made of equal parts whalebone and steel.