Last year, I had both my knees replaced with prosthetic joints – three months apart; one in February, the other in May.

The recovery was unbelievably painful, the rehab was gruelling, the night pain appalling, and for months and months, life was a grim old blur of painkillers, physio and post-operative brain fog.

By the end of the year, while the knees were working pretty well and I had finally ditched the crutches, I’d put on about 10lb, lost every ounce of muscle mass I’d ever had and was embarrassingly tentative and unsteady on my feet.

I tripped over with alarming regularity – on the flat, on hills, on holiday, on our local high street, in the office, on our garden path and, much to his embarrassment, outside my son’s school.

I was 56 but felt at least 106 and, with my clothes off, looked somewhere in between. Something had to give.

First, I tried personal training sessions at my local gym, which I loved. And a few circuits classes. And spinning. And swimming. And walking. And cycling with my sons aged 13 and 14. And eating more protein and drinking less wine and fewer very strong gin and tonics. And taking creatine and magnesium and collagen and everything else we’re told endlessly to take to make us stronger and fitter.

At 56, Jane, who had both her knees replaced with prosthetic joints in the space of three months, felt at least 106 years old – and said she looked somewhere in between with her clothes off

But it all just felt like fiddling around the edges. A couple of sessions and then a sore back; 3lb down, 2lb back up – forever bobbing around the 10st mark and looking as if I’d been piped into my favourite jeans and bursting out of my bras.

Clearly, I needed a more radical approach. A complete reboot to see if there was a slimmer, fitter and, most importantly, stronger person lurking under my 29.6 per cent body fat and feeble muscles.

If there wasn’t, I wasn’t quite sure how the next 30 years were going to pan out. Because, as we are all reminded every five minutes, building muscles is the key to longevity. That we women in our 50s must ‘lift heavy s**t’ and that our future wellbeing hangs on weights and resistance training.

In fact, as revealed by a 30-year research programme for the British Journal of Sports Medicine, doing between 90 minutes and two hours of weight training a week is a bit like a magic pill.

Because it can not only lower the risk of premature death (from any cause) by 13 per cent and reduce the chance of death from heart disease or stroke by nearly a fifth. It can even reduce the risk of death by neurological diseases – such as dementia – by a staggering 27 per cent.

So with all that ringing in my ears – and given I could barely carry a shopping bag home without stumbling about like a drunkard – when I was set the challenge by my editor to make the cover of Women’s Fitness magazine, one of Britain’s most successful health magazines, I really tried not to laugh in her face.

Jane managed to lose more than 7kg to go from 10st to 8st 12lb and reduce her body fat by 6 per cent in just four months

Jane was set the challenge by her editor to make the cover of Women’s Fitness magazine, one of Britain’s most successful health magazines and is on November’s edition, looking glossy, toned and strong

After all, we’ve all seen those women on the front. Ridiculously glossy, super-toned, lean, strong and ready to take on the world. A different species to most of us mere mortals.

But here was the chance to get properly fit and strong. To feel in control of my body for the first time in years. To look at the future with confidence. It seemed mad not to have a go.

The magazine puts me in touch with a company called Ultimate Performance, which offers what it calls a Total Body Transformation, and I meet my wonderful trainer, Emma Kershaw, who moves with the balletic bend and poise that comes, I learn later, from years in the circus as a contortionist, before she damaged her back.

We chat in a small room in the company’s gym in Paddington, west London (there are more gyms scattered around the country), with the walls lined with ‘before’ and ‘after’ pictures of big, soft, pasty fatties next to the tanned, waxed, oiled, muscular mini versions of themselves they have become. Emma is lovely and full of good news.

As she photographs my sagging body and measures my fat with cold metal callipers – a very levelling experience – she tells me how, with all the very heavy weight training we will be doing together, I will feel different, better, stronger, thinner, leaner, happier. And promises me I won’t fall over any more because, under her tutelage, I will build muscles which will actually hold me up.

Which is encouraging, because when she hands me a bottle of water, I’m embarrassed to admit, I can’t actually unscrew the lid. I’m also expected to average at least 12,000 steps a day – to act as a ‘buffer’ for bad behaviour and dietary slip-ups.

Jane says her impressive transformation is down to just eating less and better, moving more and lifting heavy weights, which immediately made her feel more in charge and stronger

Which brings me to the less good news. Because I weigh just over 10st and am only 5ft 3in, and my DEXA body composition scan shows I have a visceral fat (the nasty fat that cradles your internal organs) reading of 47cm2, I’ll have to restrict my calories to 1,433 a day, eating whatever I like, but ideally stuff that will fill me up – low-fat, high-fibre, high-protein, no booze. Or not much, anyway.

Then she logs me into an app in which I have to log or ‘track’ everything I eat, along with my steps, state of mind, daily weigh-in, and anything else I fancy – which she monitors at her end and sends encouraging messages – ‘Great fish!’, ‘Love those beans,’ and ‘Never seen anyone eat so much cottage cheese!’

If I’m honest, the diet is a boring fiddle and I struggle with it, but I love the exercise. At least four weight sessions a week – a couple with Emma, in which she’s endlessly adjusting me, pushing my chest out, shoulders down, arch your back – and several more in my local leisure centre on a programme she sets me.

It’s always less than an hour. And it always makes me feel good. Happier, more in control of my life. A bit like my old pre-surgery self. Because, over the years, as my joints started crumbling, quite a lot of things I love have fallen by the wayside.

First to go was the running. I loved it and would always pack my trainers when I was away with work. I ran 10ks and half-marathons. I did the London Marathon and an Olympic triathlon – a 1.5km swim followed by a 40km bike ride and 10km run.

Then, when I was 52 my left ankle collapsed – a mixture of a dancing injury in a Manchester nightclub in my early 20s and a genetic predisposition to arthritis – and life got smaller.

Tennis went. Along with the annual Fryer family cycling trips with my siblings and cousins. And skiing. And walking on pebbly beaches. Or sand. Or, after a while, walking pretty much anywhere at all.

Two major ankle surgeries followed. The first in 2021 to clean up the joint. I was horizontal for weeks, then on crutches for months.

But it didn’t work because there was no cartilage left to clean up, and the chronic pain of bone on bone was so grinding, I could feel myself tipping into depression.

So the following year, after pulling myself back from the brink with some pain management therapy and asking my surgeon if he’d ever had to amputate someone’s foot because it hurt so much (he had), I had my ankle fused into a right angle, effectively removing the joint. More horizontal weeks. Months on crutches.

But it worked. I joined a gym, bought a new bike, started walking everywhere again, went skiing and sent my ankle surgeon and physio triumphant photos from the slopes.

Until, in 2024, my knees went. Crunchy, swollen, chronically sore and both in need of full replacement surgery. Which my knee surgeon told me – only after the operations, wise man – is second in pain only to spinal surgery.

He’s right, the recuperation was awful because, unlike the ankle – which is just propped up with nothing to do on a soft pillow – the knee must be bent and flexed from the minute you come round from the anaesthetic. It was a dismal time. In retrospect, I was probably mad to do one knee replacement so close to the other.

And there’s a time – about a month after major surgery – when you can’t imagine ever feeling like a normal person again. Your brain goes all mushy. You have no chat or bounce or curiosity.

And you can only dream of being able to dash for a bus. Of racing upstairs for a forgotten jumper. To be strong and fit enough to go dancing with your husband, or carry the shopping, let alone lift huge weights in the gym and actually want to look at yourself in the mirror.

After so many surgeries, I didn’t really dare think that was possible. But it is. Though it’s also bloody hard work. Particularly the diet, because it turns out that, if you’re a grazer like me, who loves crisps and cheese and toast, 1,433 calories isn’t actually that much.

So out goes butter, olive oil, alcohol (mostly but not religiously because, after all, life’s too short), red meat, white carbs, salty snacks, and in comes fish, chicken, beans and a lot of high-protein cottage cheese and yoghurt. Which is hard sometimes when the rest of the family are tucking into spaghetti bolognese and Eton Mess.

At first, I feel grumpy and tired and, yes, bloody hungry. And bizarrely, and despite going to the gym every day, it takes a week or so before I lose any weight at all.

While Emma’s encouragement on the other end of the app is helpful – ‘weight loss is never linear, don’t worry!’ – and keeps me on the straight and narrow, there are downsides to this sort of dietary transparency.

Such as when I brave a big party about three weeks in.

On her instructions, I lay the groundwork with a low-calorie, high-protein meal and treat myself to a gin and slimline and small bowl of olives and dutifully log them. And then head out.

I wake the next morning, face in pillow, to a message.

‘How did the party go? You haven’t logged anything!’

And so, sheepishly, I log the second gin. And five cans of Tiger beer. And I remember the trays of sausages in honey and mustard that came out late at night. And the sour cream and chive dip with mountains of nachos. And the mountain of brownies. And when I log all that, Emma goes very quiet for a bit. And then, finally, she replies.

‘OK… let’s not panic.

Maybe no more beer until we’ve finished.’

The 12,000 steps are much easier and make me feel better about the sausages and brownies – walk everywhere, get off the Tube a couple of stops earlier. Pipkin the dog gets an extra late-night walk and can’t believe her luck.

And the weights are just brilliant. Chest presses. Push-ups. Rowing. Deadlifts. Almost immediately, they make me feel more in charge. More able. Stronger. Straighter.

The key, I learn, is doing them properly. I am lucky enough to have Emma constantly adjusting me and pushing me on, but most leisure centres have decent gyms and an introductory session where staff will show you how to use the machines and set a training schedule.

And that’s really all there is to it. It’s not brain surgery. You don’t need to spend a fortune. Just eating less and better, moving more, and lifting heavy weights.

Oh yes, and I take a few supplements, but nothing fancy and nothing you can’t get in Holland & Barrett – two daily tablets of magnesium, because as well as encouraging sleep, it helps your muscles recover quickly; creatine (a white, tasteless, powder that dissolves in water); vitamins D and K and some fish oil tablets for my joints.

But it works. Over four months – with a few blips and slips and the odd gin and tonic here and there, I lose over 7kg (16lb) to go from 10st to 8st 12lb. I reduce my body fat by 6 per cent to 23.4 and my visceral fat plummets to 35cm2.

My before-and-after DEXA scan shows that my bone density has actually gone up by a couple of per cent – so unusual for a woman my age that Arthur at Scanletics where I have my scan gets really quite excited about it: ‘This is exceptional Jane, you should be very proud of yourself.’

I am. And along the way, there have been some brilliant milestones. The first person to say, ‘Wow, you look well. Sort of different. Taller?’

The woman in the gym who asks if I’d been on the jabs.

The ridiculous pleasure as the weights get heavier, my pre-kids jeans fitting again and my prosthetic knees starting to feel like my own.

Not forgetting these extraordinary photos for Women’s Fitness magazine which look like someone else – glossy, toned and strong – but somehow, just four months later, are actually me.

But most of all, the dawning realisation that I’ll keep going with much of this. The steps, the veering (mostly) towards high protein, the lower-calorie food and, yes, less alcohol and particularly the weights.

Partly because it is now very clear to me that I will live longer and better and be a lot happier if I do. But also because I love how it makes me feel – strong and confident and, dare I say it, really rather pleasingly lean.

Just as my four months end, I head off on a four-day Fryer family cycle ride – 175 miles from Morecambe to Bridlington, with siblings, cousins, nephews and elder son Freddy. The first for more than ten years and exactly a year from my second knee replacement.

It feels amazing, incredible, really rather emotional and I nearly weep as we pedal through the Yorkshire Dales in the sunshine and Freddy shouts across at me: ‘You’re doing really well, Mum! And you know, I’ve just realised, you haven’t fallen over in ages!’

The November issue of Women’s Fitness is out on Friday.