In 2022, Caroline Idiens was on holiday halfway up an Italian mountain when her brother called to tell her to check her Instagram account. “I said, ‘I haven’t got any wifi. And he said: ‘Every time you refresh, it’s adding 500 followers.’ So I had to try to get to the top of the hill with the phone to check for myself.”

A personal trainer from Berkshire who began posting her fitness classes online at the start of lockdown in 2020, Idiens, 53, had already built a respectable following.

But after one video offering guidance on getting toned summer arms was picked up by a US fitness account, that number rocketed to 50,000 – and beyond. “I post it every year now as a bit of a tribute,” she jokes. “It was that reel that launched me into a whole new market.”

Today, as @carolinescircuits, she has 2.3 million followers on Instagram, more than 70,000 on Tiktok and 50,000 on YouTube, and a book, Fit at 50, that was a recent Sunday Times bestseller – making her a key influencer in an increasingly important demographic for social media platforms: those in midlife and older.

If you want to grow your reach on social media, figures suggested this week, you could do worse than target the over-55s.

Research from media analysts Ampere found it was people in the 55 to 64 age bracket who were delivering the highest growth in YouTube traffic, up 20% since 2020 in the US and 14% in the UK. Tiktok, too, has had a 16% rise in British users in this age bracket in the past year.

“We’ve been seeing this trend over the last few years where older audiences who have traditionally [focused on] linear and broadcast TV have been digitising,” says Minal Modha, the head of Ampere’s consumer research division.

“And by getting access to things like smartphones and smart TVs in particular, it’s opening up a whole new world for them.” More than half of US adults in the age bracket now watch influencer videos weekly.

Some of them will be tuning in to Valerie Mackay from Inverness, who as @embracingfifty has gained 312,000 followers on Tiktok and almost 1 million on Instagram since she started her warmly chatty account eight years ago.

“In hindsight, I wouldn’t have picked that name ’cause I’m now 62 and stuck with it. But the point of the name was I was embracing life over 50. I had two children, they had both left home and I was enjoying life with myself and my husband, it was like freedom.”

She founded her account after overhearing a woman asking what was the point of makeup and style after a certain age. “I just thought, well, what’s the point in life? Just dress and be who you want to be.”

Mackay says she tries not to think about the huge numbers watching her from around the world – many of whom share an interest in the Scottish weather.

“I get asked a lot: ‘I’m coming to Scotland, what do I wear?’ Which it’s difficult for me to answer because I might be flitting about in a trench coat and they might need big coats.”

Mark Lidster is a 62-year-old from north London who posts videos as FitnessGeezer on YouTube and Instagram, attracting up to 1m views. “There are a lot of guys out there getting to 40, through to 70, 80 – who relate and take inspiration from what I’m doing,” he says.

Like Mackay, Lidster says actively engaging with his audience is crucial. As well as becoming more savvy with tech, he says, “people of that age are feeling more disconnected from society, and getting lonelier. Social media is another way of feeling part of something – I try to create that community feel.”

The crucial thing with 50-somethings and older is “to keep it genuine”, says Idiens, who is 53.

“The biggest thing about social media in this age bracket is trust,” she says.

“It has to be genuine – we are a little bit older and wiser, and what the audience are really looking for are people that they can trust with advice. For the midlife demographic, they also really love that sense of community.

“Even with an audience of 2 million, I still think, when I’m putting up a post, that it’s going to my friends and family group. And the feedback I get is that [my followers] still feel like I’m a PT [personal trainer] in their sitting room – which, for me, is everything. That’s what I want.”