It’s late afternoon on one of summer 2025’s drizzly days and, on the floor of her kitchen, Caroline Idiens is attempting her first crow pose. That the triceps belonging to the 53-year-old PT are among the most famous in the business is one reason I suspect her beginner status will have little bearing on her ability to hold her own body weight; her quiet confidence, another.
‘I love a challenge,’ she tells me, taking a sip of her tea before crouching on the floor to begin.
Moments later, she’s hoicking up her Me+Em trousers, pushing her palms into the floor and lifting her feet off the ground. Her body is suspended in the air for several seconds before she returns to earth – and her place at the table beside me. High-fiving her, I joke that a) it’s payback for the dumbbell donkey kicks she had me do in her full-body class earlier this week and b) the pose I’ve just talked her into trying is a neat metaphor for her meteoric rise: strength gives you wings.
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In the unlikely event that you’re unfamiliar with the woman better known by the name of her wildly successful fitness platform, her formula of four 30-minute online classes a week has earned Caroline’s Circuits 6,500 monthly members, most of them in midlife, and propelled her into the feeds of 2.3 million Instagram followers. For context, that’s even more than former cover star and fellow poster woman for midlife fitness Davina McCall.
‘It’s crazy,’ she tells me. ‘When the numbers come up on screen, I have to not look.’ I was one of 1,500 doing that workout on Monday, streamed from her Berkshire living room in front of her Neptune sideboard and Oka lamps (‘everyone asks me about the lamps’), with guest appearances from Tilly the cocker spaniel and a labrador called Pip.
It wasn’t the first time I’ve had a glimpse into Caroline’s world. She and I began our fitness platforms around the same time – mine, Rocket Yoga; hers, circuit-based strength training – exchanging lessons and learnings along the way. And in five short years, I’ve watched her go from a jobbing PT to a global fitness icon.
She first went viral with an arms workout in 2022, then again with a workout using water bottles as weights, which she improvised while on holiday in Corfu. She’s been crowned the ‘workout queen of middle England’ by the Daily Mail, declared a midlife fitness guru by The Times and I suspect fronting this magazine’s annual issue dedicated to the pursuit of ageing well will only serve to cement her status as one of the most influential women in fitness right now.
What is it about her approach that women are so drawn to? ‘The fact that it’s at home,’ she tells me, without missing a beat. ‘People say it feels like [having] a PT in their sitting room. They may be someone who’s too intimidated to go to a gym, so they really want to do this online, at home. And not only am I doing the classes with them, I’m there as support. So it’s about creating that connection – and I’ve been doing that for 20 years.’
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Circuit training
Ah yes, experience. It can be all too easy to gloss over the grind that predates an Instagram presence. But, like any woman entering a new phase of her career in her fifties, the ease Caroline brings to her classes is earned.
She was in her late twenties when she first caught the weights bug. An account director for an advertising agency, her workouts probably looked a lot like yours in the ’90s (‘cardio – just running on a treadmill for 60 minutes, so boring’). Until she found a class that changed everything – first her body, then her mind.
‘It was Les Mills Body Pump, which was 45 minutes of lifting weights, led by an instructor and I absolutely loved it. It was the first time I’d lifted weights and the thing I loved wasn’t just how it changed my physique, but the feeling that I got from being stronger – the sheer confidence it gives you in what your body is capable of. It’s your posture, the way that you walk, the way you carry yourself.’
The class led her to private PT sessions where, over conversations about progressive overload, she discovered a passion that ran so deep she decided to make it professional.
‘I just thought, “Right, it’s going to be a bit of a gamble giving up quite a good advertising career.” So I wanted to do a course that was about more than fitness – sports, rehab, nutrition, all of it – so I could learn how the whole body works.’
A year of living off savings and one PT qualification later, she was leading 5am classes in Hyde Park. And after meeting her husband (who works in the beauty industry), having children (a boy, now 19; and a girl, 17) and moving to the shires, pre-dawn sessions with professionals evolved into post-school-run classes for parents; one of them named their WhatsApp group ‘Caroline’s Circuits’ – and the name stuck.
But it was a pandemic-era pivot to digital training that catapulted Caroline from a local PT with a loyal following to a national, then global name. As the first lockdown loomed, she took her classes online after a client suggested it. And the word-of-mouth PT who didn’t have a website, let alone a link in bio, found herself retraining once again – this time, in digital marketing.
Was she, like me, having to teach herself a whole new language?
‘Yeah – I had one session with Instagram where it was like: what’s a hashtag? But then I was completely self-taught. I’d worked in advertising, of course, but we didn’t do social media marketing back in 1995, so I had to learn very quickly what works and what doesn’t.’
An early learning was posting every day – which she did, for five years (‘except Christmas Day, the day the Queen died and my birthday’).
She also learned to listen, creating content that spoke directly to the questions filling her inbox on the daily; questions such as, ‘How do I actually do a press-up?’ ‘How can I modify a squat?’ and – the most common one – ‘How do I actually start strength training?’
Compound interest
Half a decade later, it’s a skill that’s served her well. But personally responding to 300-plus daily DMs has also gifted her privileged access to the ambitions and ailments of midlife women.
‘Preserving muscle, looking after joints, the balance of cardio versus strength training and thinking about bones and osteoporosis [a condition characterised by the thinning and weakening of bone, often caused by the loss of oestrogen during menopause],’ she tells me, when I ask what women want from her workouts. ‘I get women sending me their Dexa [bone-density] scans. These are women who’ve been told they have osteopenia [a precursor to osteoporosis]. They haven’t changed anything else, but doing these workouts consistently has made a real difference.’
Consistency is key; that she’s been lunging and lifting for more than two decades herself is one reason she suspects she hasn’t yet been advised to start taking HRT, an evidence-based intervention for both preventing and treating osteoporosis and the primary treatment for myriad menopause symptoms.
‘At the moment, I’m just not at the stage where [my symptoms] are impacting my daily life. But that’s not to say I wouldn’t take HRT in the future and I know it helps so many of my friends, colleagues and members.’
If strength training with your skeleton in mind is one non-negotiable in the midlife fitness protocol, banking muscle is another.
‘Muscle banking! I love that,’ she says, when I joke that muscle mass is the new pension fund. We talk about the fact that skeletal muscle – the fibres attached to bones responsible for movement – is acquiring revered status as ‘the organ of longevity’, with quad strength in particular being positioned as a predictor of lifespan.
‘Which makes sense when you think about independence and mobility… it’s why I think squats are the number-one compound exercise [moves that work multiple muscle groups] from a longevity perspective. A lot of people would say deadlifts, but if you’re thinking about getting in and out of a chair when you’re 80, it’s squats.’
Not that you need to be in midlife to start preparing for later life.
‘I think what’s exciting is that this conversation about preserving healthy skeletal muscle and building up your muscle as a kind of armour as you age is now being had by younger women who are thinking, “Why wait?”’
Thirtysomething women are subscribing to her platform in growing numbers and the trend is playing out close to home too.
‘I’ll go and watch my daughter play hockey at school and they’ll be doing strength and conditioning sessions before their matches – squats, planks, press-ups. They’re 17 or 18 and they’re all lifting weights – I just love that because we weren’t thinking about this stuff at all back then.’
We really weren’t. When she and I were in our twenties, doing a workout for your future self was less about fitting in another 10 years, more about fitting into a pair of jeans. But while we might like to think we left exercising for aesthetics in the ’90s, the topic is alive and well on social media.
‘Overnight six-pack, the snatched waist and the bikini body,’ she says, reeling off some of the ‘quick fixes’ that have riled her up recently.
What about the other topic currently dominating the dialogue? That everyone I know seems to know someone using GLP-1 medication to manage their weight means I’m surprised to learn they haven’t reached Caroline’s DMs.
‘I think those who follow me are primarily interested in looking at their health from an exercise perspective,’ she tells me, with the caveat that side-effects of rapid muscle loss are ‘a concern for those already experiencing muscle loss if we think of how this loss will affect these people in later life’.
Still, her audience is at an age and stage when body composition is often front of mind, meaning weight loss is a common goal.
‘A lot of them are hugely frustrated by weight gain in menopause,’ she confirms. ‘So we’ll talk about the fact that they’re not alone, that the decline in oestrogen means the body holds on to fat around the middle and the value of strength training at this time.’
(One of oestrogen’s many roles is in fat distribution; when levels plummet during perimenopause, fat storage tends to shift from the hips and thighs to the abdomen.)
She doesn’t promote her platform as a tool for aesthetic engineering (‘for me, it’s about trying to move away from how you look and focusing instead on how you feel’). But nor does she shy away from celebrating the confidence that an aesthetic shift can deliver.
‘One woman wore a sleeveless dress to her son’s wedding and the fact that she had her arms out and felt so confident just made her day – I loved that.’
And during a life stage when hormonal havoc can make your inner critic roar, it’s the confidence current account that can feel like the biggest payday, even more so than the muscular pension and skeletal ISA. It does for Caroline.
‘I’m definitely more confident in my shape now than ever before. And I noticed that when I was on holiday – because on a holiday, you’re always quite critical about how you look, aren’t you? And I think, actually, I just feel, at this age, probably the best I’ve felt.’
Rest and digest
The good news is that the formula that supports such solid foundations both inside and out is entirely poachable, at least from a training perspective.
‘I get asked that all the time,’ she laughs, when I become the latest person to enquire after her own workout week, before confirming that, yes, the four workouts she films each week are the only times she lifts weights.
The 30-minute model is a product of the time poverty that afflicts every woman I know, while the circuit model is an adaptable one (‘upper body, lower body, you can fit it all in’).
‘But doing exercise for short periods of time with shorter rest periods also has brilliant long-term effects for building muscle, specifically in midlife.’
Monday is a full-body session, it’s arms and abs on Tuesdays, legs and glutes on Wednesdays and a strength-HIIT hybrid on a Friday. And there’s a reason she resists calls for classes seven days a week.
‘The days that you don’t train are as important as the days when you do – that’s when the muscle changes, that’s when the growth happens.’
Her own rest day is Saturday, but that doesn’t extend to work (‘I love to get up before everyone else, make my coffee and plan what’s coming up next week’), her Sundays invariably feature ‘some stretching, some walking – we might go out and play tennis and the kids are getting me into padel’.
Her approach to nutrition was already well seasoned when she published her book, Fit At 50, back in March. But since working with dietitian Laura Clark for the book’s recipes, she’s been trying to eat more fibre (she loves lentils) and plant-based protein (quinoa is in regular rotation).
‘It’s about making protein the king of the meal, but not worrying about the exact number of grams you’ve had.’
It’s a common-sense approach that extends to alcohol, too.
‘If I go out for dinner, I love a gin and tonic. But I’m not a big wine drinker – I’m up at 5am…’
The wake-up time – necessitated by her Instagram posting schedule – is one reason quality sleep is top of the agenda. But it isn’t the only one.
‘I think my screen time is why my sleep is so useless. I know I’m up way too late on my phone, so my target for this year is to get to bed and try to get seven hours.’
Plans are afoot in her waking world, too.
‘I’ve got one child going off to university and one going into her final year of school, so it’s about quality family time during the summer.’
And now that summer 2025 is a wrap?
‘Meet-ups, events, retreats,’ she shares, of her plans for the platform. But there’s plenty to keep her busy in the here and now, too.
‘September is the new January for me. It’s when everyone wants to get back into a routine after being off with the children or off work.’
And more than viral winds and algorithmic alchemy, if there’s one thing that keeps women returning to her workouts, I suspect it’s this:
‘It comes back to the fact that I’m 53. I really am of this demographic… I’m not 20 years old and doing these workouts in a studio. I’m in my family living room, doing it with them – and I’m telling them when it’s hard.’
In crow pose and every other.
To sign up, visit carolinescircuits.com
Hair: Alex Szabo at Carol Hayes Management using Maria Nila
Makeup: Sam Cooper at Carol Hayes Management using Lisa Eldridge
Set build: Cloud & Horse
This feature appears in the October 2025 issue of Women’s Health, out now. You can subscribe to Women’s Health here.