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I am not enjoying this form of exercise. Really – I’m not. My heart is pounding, I feel sick in the stomach, the sweat is beginning to prickle on my arms and shoulders, and my hands are trembling. It’s my very first blog posting.

But that’s nothing compared to the exercise that’s facing four members of the great and the good over the next six weeks. They’re going to be prodded and poked, measured and weighted, bullied and sweated. They’re going to tone up their bodies, lose pounds of fat (but hopefully none of their dignity), and try to eat and drink properly. All in a good cause.

The Daily Politics on ³ÉÈËÂÛ̳ Two is filming three MPs and a baroness as they take part in a diet and fitness regime to help themselves shape up, and lead the way in tackling the obesity crisis facing Britain. From Monday until the end of June the Daily Politics cameras will follow them as they get training instruction from the formidable Body Doctor, David Marshall at his London gym. And from what I’ve seen so far, it’s looking great.

The highlights are the agonies of the MP, Mark Oaten. You remember him - home affairs spokesman for the Liberal Democrats, family man and would-be leader of the party, whose affairs with rent boys were exposed earlier this year.

Why’s he doing it? Well, there’s a relationship between absolution, pain and humiliation: think hair shirts, pilgrimages on one’s knees, and self-flagellation. So I think it’s an act of penitence. Others think it might just be cheap publicity as part of a hopeless attempt at a comeback. But this is what Mark himself told us: "Exercise is a way of cleansing the brain – it’s a mental health thing and I want to learn how to do that."

Whatever his reasons, he is suffering. He’s trying to give up chocolate. He’s got to limit and improve his eating and drinking. And his regime is a punishing one: an hour-and-a-half three times a week for six weeks. Each visit he’ll do a 15-minute warm up, a 45-minute full body workout involving all the muscle groups, and a 30-minute cardiovascular session. At one point in his first session he – nearly – couldn’t take it. He was on his knees whimpering.

Although Mark has rather hijacked the attention surrounding the series – with a series of interviews to the media about how its all part of his comeback from hair loss – the films are actually about much more than him.

There’s Sailesh Vara, the fortysomething Tory MP from Cambridgeshire, who used to hold a black belt in a martial art in his youth, and who’s trying to recapture the glory days of his six pack and 30-inch waist. He wants his constituents, the Indian community and Conservatives everywhere to take up the health message.

With him is Meg Hillier, one of the new intake of Labour MPs, who’s 37 and from Hackney. She’s well up for it, and her plan is to get rid of her "mummy tummy", and push the health message through to kids everywhere. Though she’s quite fit, she’s also finding it very tough.

Then there’s Susan Greenfield, the svelte barnoness with the big brain, leading scientist and member of countless academies, who at fiftysomething is the oldest of the group, but the one with the fewest pounds to shift. For her it’s about getting the more-than-middle-aged to understand how diet and activity can keep you feeling younger and healthier.

They’re all as interesting as Mark Oaten in their own ways.

But perhaps the real star is the Body Doctor himself – David Marshall, trainer to sports starts, celebrities like Ant and Dec, and now MPs. His very high tech gym in Chelsea is the base of all operations. And his approach puts the toughest chief whip and most acerbic Speaker to shame.

How's this for a manifesto pledge: ‘The end product is the empowerment of the individual and their complete and utter belief and knowledge that they and not us have been the primary factor in their physical mental and emotional improvement." He’s devised the punishment, he’s a tartar, but he’s also very good.