'I wasn't prepared - that's where my weight gain started.
'When you're a professional athlete, you're in this bubble that's not reality - everything is done for you … training, food, travel, management, so going back into real life was very different.'
Jelena went on to reveal that her battle with glandular fever, a thyroid condition and glandular fever also contributed to her weight gain. But having already lost 21kg, Jelena says she’s planning to lose another 33kg in 2019.
She’s already been taking to Instagram to reveal her weight loss journey, posting inspirational messages to her many followers.
'Today is my tomorrow. It's up to me to shape it, to take control and seize every opportunity,' she revealed in one of her posts.
'The power is in the choices I make each day. I eat well, I train, I live well. I shape me. It comes down to one simple thing: How bad do you want it?
'Because I want it really bad and I will get it.'
Jelena is also planning to marry her boyfriend of 15 years Tin Bikic in the near future, and would love to start a family.
It’s a stark turnaround from her troublesome tennis career, where she allegedly suffered abuse at the hands of her father.
In 2017 book Unbreakable, Jelena says the worst beating she ever endured was after losing at the 2000 du Maurier Open in Canada.
'It was a really nasty memory that will stay with me forever… I ended up fainting,' she recalled. 'He beat me really badly.'
She’s now determined to turn her life around - both mentally and physically, and has never looked better. Go Jelena!