Jessica Simpson lost 100lbs by changing her diet.
The 39-year-old singer ballooned to 240lbs when she was pregnant with her now-seven-month-old daughter Birdie but managed to get back to her pre-baby weight in six months thanks to some help from her trainer Harley Pasternak, who helped her to overhaul her diet.
He told Us Weekly: "It's not about the workouts. You don't lose weight doing biceps curls and lunges. You lose weight by changing your diet, hitting your step goal, working on your sleep ... those were the things she did so well."
He also revealed that Jessica follows the principles of his 2013 book, 'The Body Reset Diet' and had three meals and two snacks a day with protein, fiber and healthy fat.
Jessica previously said she was working "really hard" on her body by walking lots and eating healthily because she wanted to feel "good" in her own skin.
She said at the time: "I am working really hard right now. It's not easy at all, but I am determined to feel good.
"I have been doing a lot of walking - getting my steps in not only burns calories but it also helps me clear my head and get focused. I am eating healthy too - I discovered I really like cauliflower. Who knew it could be a substitute for almost anything?"
As well as working on her post-baby body, the 'With You' hitmaker - who also has Ace, six, and Maxwell, seven, with her husband Eric Johnson - was trying to find a way to juggle being a mother to three children.
She explained: "Three kids is no joke. It is definitely constant, and the biggest challenge for me is trying to be present when I am pulled in so many directions. They are all in such different phases now."
