"I didn't want to go out of the house and I even turned down work opportunities because I was so insecure and unhappy."
Dokic added: "It's not just about weight loss either but about having a healthy and balanced lifestyle and developing healthy but sustainable habits for the rest of your life.
"While I don't want to talk about the kilos too much, I have lost almost 20 kilos between the second and third picture alone.
"I hope I can inspire and motivate you all. No matter what you are trying to achieve, it can be done.
"I am halfway on my weight loss journey and very excited about what is ahead."
Dokic also said she hopes her story will inspire others going through similar struggles.
"I thought I would brave the judgement, negativity and scrutiny that sometimes comes with being in the public eye and on social media and put myself and my struggles out there and hopefully inspire, motivate and help others, especially women," she wrote.
The 2000 Wimbledon semifinalist opened up last year about having "suicidal thoughts" after being abused by her father as a child, which was revealed in her autobiography Unbreakable.
Earlier this year, she said retirement had left her feeling "lost" which led to her to gaining weight through emotional eating and a lack of life structure.
"I was thrown into retirement not knowing what direction I wanted to go in," Dokic told the Herald Sun in January.
"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."
Dokic says the release of her autobiography, where she revealed she suffered physical abuse as a child and teenager almost every time her father was displeased with her performance on the tennis court, was a cathartic experience which helped her get on top of her weight.
"The book released a lot of emotions I was holding in for a very long time," Dokic said.
"I'm happy with what I have, but (my weight) is the missing piece in the puzzle."
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call 111.
If you need to talk to someone, the following free helplines operate 24/7:
DEPRESSION HELPLINE: 0800 111 757
LIFELINE: 0800 543 354
NEED TO TALK? Call or text 1737
SAMARITANS: 0800 726 666
YOUTHLINE: 0800 376 633 or text 234
There are lots of places to get support. For others, click here
