MY personal trainer is pleased with my improved flexibility and movement.

I never thought I would say such a thing. Because I would not spend money on a luxury like a lifestyle adviser. And I am not keen on exercise beyond a gentle stroll or a splash about the swimming pool.

But a familial well-wisher - as in someone who wishes me to be well - has funded me for a 10-week session at DMC Fitness.

So here I am in a gym in a nice basement off Glasgow's Sauchiehall Street. It is relatively tranquil, with just a handful of people, unlike the zoo ambience of big health clubs. Tranquil, that is, if you don't count the man pounding on a lorry tyre with a sledgehammer.

My coach is Pablo, from Paisley, who weighs me in at 15 stones. That's a stone or so lighter than my heaviest ever, the weight shed due to dietary changes to combat Type 2 diabetes. The target is to get down to 13 stones.

In one corner of the gym the sledgehammer man, who is about my age but trim and muscled, is doing what I can only describe as press-ups without hands. In the other corner Pablo is assessing my fitness by putting me through some stretching exercises on a mat. The assessment is that I am so unfit I can barely get down and back up from the floor, never mind stretch muscles that have been neglected for decades.

I am embarrassed, so what do I do? I borrow a marker pen and correct the misspelling of "success" in the handwritten motivational message on a whiteboard on the wall. I also delete and add apostrophes as necessary.

It comes as no surprise when I get a low score as I fill in the Client MentorAbility Index in my personal dossier. It has statements such as "I do what I agree to do without struggling or sabotaging" and "I am prepared to try new concepts I may not feel comfortable about".

My rating is the lowest level on the index: "Not very coachable right now." There will have to be mental as well as physical adjustments if I want to be fitter and slimmer. Mr Sledgehammer, who Pablo tells me used to be overweight and unable to exercise because of a bad back, is hanging upside down on a frame doing chin-ups or chin-downs or whatever. I now call him Mr Motivation.

What you get with a personal trainer is support and endless patience. Pablo puts me on a regime of warm-up exercises and some resistance work to improve flexibility and movement. If I persevere, one day I will be able to do the no-hands press-up which, I see from my dossier, is actually called the Skydiver. And maybe have a go with the sledgehammer, one of a number of exercises that replicate the exertions of a hard day's work.

The 16 separate mobility warm-up exercises include a Mexican wave, doing the Charleston, a Tommy Cooper bit where you flick your wrists, and some pelvic thrusting. I now do this routine in my garden, on the beach at Barcelona, and in the Turkish room at the Arlington Baths Club. Except for the pelvic thrusting, which can be misconstrued by onlookers and is best done in private.

I still get stiff and sore from my exercises but the recovery time is getting shorter. I find it easier to put on socks, tie shoelaces, and get up and down from the floor.

Exercise is not enough without a proper diet. The DMC nutrition regime is rigorous. No sugar, no dairy and very little of the dodgy carbohydrates that bloat the body. Almost no caffeine or alcohol.

Cooking is to be done according to the Paleo diet, which is caveman style. None of your modern processed foods but plenty of green vegetables, fish and lean meat. There are plenty of options but strangely I have come to love cabbage, spicing it up with cumin, black pepper, Moroccan harissa or horseradish.

Such staples as bread, pasta and rice are to be avoided. A healthy curry is consumed with a rice substitute made from cauliflower. There is also a green supplement that smells and tastes a bit like the contents of an ashtray but is okay mixed with beetroot and apple juices. Some fasting is involved but also a day when you deliberately overeat.

Hunger pangs are assuaged by eating a few nuts. Who needs a KitKat when almond and coconut cookies are on the menu?

It is the kind of diet I spent my whole life avoiding. But it works. Despite too frequently straying from the path of righteousness, I have broken the 14-stone barrier. Being slimmer, sadly, has not yet made me irresistible to women. Must be the cabbage.

The other important aspect of the DMC experience is the power of positive thinking, something I was never sure about before. With more emphasis on exercise and nutrition in life, I find myself being carried along on a path away from self-deprecation towards self-esteem.

I make fewer saboteur jokes. Like asking Pablo: if the Paleo diet was so good, why did cavemen have such short life expectancy? Or musing if Dave McConnachie, the imposing ex-army man behind DMC Fitness, might have been in the Waffen SS and not the Scots Guards.

I have to learn to love life in the gym. Believe that slogan on the wall that sweat is my fat crying. Pursue resistance exercises rather than resistance to exercise. Pablo has taught me that you can't kid your personal trainer and there is no point in trying to kid yourself.

You will be asking how much it costs to have a personal trainer. I didn't ask since it was a gift. But it is obviously not cheap since there is a section of the coach ability questionnaire that says: "I can afford the fee and will not regret or suffer about the fee. I see coaching as worthwhile investment to my future fulfilment in life." The cost is probably a lot less than most people's weekly spend in pubs and on excess food.