One dietitian, Kate Save, told Daily Mail Australia she estimates Rebel has lost around 18 kilos so far.
Here's how Rebel has managed to shed the kilos, according to the actress' Instagram and her celebrity personal trainer Jono Castano Acero.
Weights and HIIT
Rebel likes to mix up her workouts by doing weight and HIIT sessions, both of which have been proven effective for weight loss.
Her workouts include lifting tires, rope training, medicine balls and boxing sessions, with her trainer writing on Instagram earlier this year that the actress had been putting in solid hours.
"@rebelwilson has been putting in the yards 7 days a week! Proud of you gurl," Jono wrote in January.
According to a study published by the British Journal of Sports Medicine last year, people doing HIIT sessions will lose 28.5 per cent more weight compared to those doing other forms of exercise.
Slow and Steady
Since beginning her fitness journey at the end of last year, Rebel's progress has been steady rather than focusing on fast results.
In a since-deleted Instagram post shared in May, Rebel said her plan was to get down to 75 kilos by the end of the year.
"I'll be honest with you guys – with my "Year of Health" mission I'm trying to get to 75kgs and career wise am trying to get one of my movies into production before the end of the year! Both of these things are requiring a daily effort and there's constant set backs – but I'm working hard," she wrote at the time.
It's an approach her trainer Jono favours, telling Yahoo in an interview that diets and programs that promise results in just weeks aren't realistic for the long term.
"I think with any type of transformation, you shouldn't always look at the easiest option, you know, two months is not enough time to be able to change your body," he said.
"A transformation is never ending, the journey always continues, so you can never give yourself 10, 12 weeks. Because it just continues, once you reach your goal then what? Then you're going to stop? You can't stop it becomes a lifestyle, you continue and you become the best version of yourself as cliche as it sounds."
The Mayr Method
According to People, Rebel's health journey began last year with a visit to Austrian wellness centre ViaMayr.
While there, the star reportedly got "amazing results" following the Mayr Method diet plan of eating high alkaline whole foods very slowly, aiming to count out 30 chews per mouthful.
Active Rest
Rebel isn't just getting fit in the gym, she's also heading out for walks and hikes with her mates.
The actress shared photos of her hiking around Sydney's Palm Beach as well as enjoying a sprinting challenge at the Sydney Opera House stairs.
Jono told Yahoo he recommended people do five workout sessions per week and focus on recovery for the other two days.
"I always think of it as the more you do the better, but don't over do it. So, for any type of transformation I'd definitely recommend five times a week, with two days of recovery if possible," he said.
"But recovery is, you know, you're focusing on your stretching, getting a massage, or decreasing the load of the exercises, so, for example, going for a walk.
"Not every training session needs to be 100 per cent, as long as we're moving and we're burning calories I think that's the key for any type of training."
