Jazz Carlin's body had been dropping hints about retirement for a few months before she called it a day – she was expecting that, Olympic-level swimming is traditionally a young person's game.

What she was not expecting was what her body started telling her after she quit.

"As a swimmer, I had got very used to seeing my body look a certain way and now it was changing and not, I thought, in a good way," she said.

"Clothes weren't fitting me any more and I didn't want to step on the scales or show my body in a swimming costume – I felt a bit ashamed.

"People could tell me I looked good and healthy, but I didn't feel it."

Carlin, who won two Olympic silver medals in 2016, as well as Commonwealth and European titles, was talking to Press Association Sport during Mental Health Awareness Week, which finishes on Sunday.

This year's theme is 'body image' and it is something the 28-year-old has been grappling with ever since she stopped training like an Olympian.

As a distance swimmer, Carlin was conditioned to ploughing up and down the pool for hours at a time, the water sculpting her body. She was also used to eating a lot. The one necessitated the other.

This is a balancing act every endurance athlete will recognise and it is an equation that will produce different results if you tweak the variables, as Carlin discovered. What was once hard and sleek, became...well, softer and rounder.

"I was pretending everything was fine but I was struggling," she said.

And then she spoke to a good friend who had just had a baby, a body-changing experience that many women can empathise with.

"She said something really important: whenever you leave a mirror, do it with at least one positive thought – that really resonated," explained Carlin.

So, with her confidence returning, she decided to post a picture of herself in a bikini on social media.

"That's men and women: men might not admit these things as readily as women but it's exactly the same issue. I also hear from people who won't go on holiday because they don't want to be seen in a swimsuit.

"It often doesn't matter what people to say to you: it's what you feel about yourself."

The level of service Lindsay provides is not exactly cheap – a 12-week course starts at £3,200 – but it is less expensive than going under the knife and almost certainly better for your body and mind.

"Whatever goal you are aiming for, being stronger crosses over," she said.

"Riding a bike, swimming quicker, running faster, you will get fewer injuries and every step will be easier. And that applies at every age. I see 60-year-olds who cannot get out of chairs but leave here ready for a triathlon."

Lindsay does not actually like the "transformation tag" or the "before and after" pictures that are marketing mainstays in her business; she wants people to leave her gym feeling stronger, physically and mentally, and that can be very personal.

Or as Carlin put it: "I'm not going to punish myself for looking a certain way. I don't need to look like an athlete to feel good about my body."

– Now in its 19th year, Mental Health Awareness Week is organised by the Mental Health Foundation and it runs from May 13-19.