Simpson causes stir with skinny snap

Jessica Simpson. Pictire: Jessica Simpson/Twitter

After photos emerged of Jessica Simpson looking shockingly thin earlier this week, sources are now revealing the lengths the starlet has gone to slim down.

The WeightWatchers spokeswoman is said to have lost almost 30kg since giving birth to her second child Ace last June and insiders say she has been working extremely hard to tone her figure.

"Jessica has gotten her best body ever. She truly feels like she's in better shape than she was in her early 20s," the source said.

"She set out to get the best body of her life - and she's accomplished it."

Simpson, 33, is gearing up to marry fiance Eric Johnson in July, with whom she also has two-year-old daughter Maxwell, and friends say she is spending hours at a time on the treadmill.

"She'll watch TV on it, talk on the phone. Jess probably spends half the day there . . . She's incredibly proud of the way she's stayed on track," the insider said.

However, some are questioning whether Simpson has taken her weight loss too far after she posted a series of pictures to her Instagram account that show her looking gaunt and sporting dramatically muscular thighs.