Jazz'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.”
"We found that 1 in 5 UK adults felt shame and 19% felt disgusted because of their body image in the last year.”
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.
‘The truth is - Since retiring from competitive swimming, I’ve not really felt comfortable being in a bikini or a costume. People would say to me ‘You look really well’ but when I looked in the mirror I just didn’t like what was looking back at me.
'I’ve been so used to seeing my body the same way for so many years and having to stay fairly lean for swimming. Now that I’m not training in the same way, my body has changed so much and I can’t fit in to some of the clothes that I did before, which has knocked my confidence a bit.
But now I’m actually starting to embrace how I look, being happy with how I am and that I don’t need to look like an athlete to feel good about my body.
I’m still trying to find the right balance between my love of food and doing some kind of exercise but I’m getting there and I’m not going to punish myself for not looking a certain way. ✌' @JazzCarlin on instagram
Alongside the picture she wrote a few lines to explain why she was doing it. She wrote that she had lost the lean body of a swimmer and it had initially knocked her confidence but she was “starting to embrace how I look”.
The Twitter version of the post received more than 2,700 likes and dozens of comments, including supportive messages from several former Olympians who knew exactly what Carlin was going through. She also got dozens of compliments about how good she looked.
Born in Swindon, Carlin grew up in Swansea and won gold for Wales in the 800 metres at the 2014 Commonwealths in Glasgow (Andrew Milligan/PA)
“I really pondered over the post and wondered whether I should do it,” the Swindon-born swimmer told the Press Association.
“I was worried people wouldn’t understand it and would think I was just looking for compliments. But the truth is I hadn’t been happy with what I was seeing in the mirror.
“But I am really pleased I did post the picture because I got some amazing messages back from young girls who have struggled with their body image and ex-athletes who have been through exactly the same thing.”