Lawson, who has two children with her first husband, late journalist John Diamond, recently credited her youthful looks to avoiding sun exposure and eating "lots of fats".
She also previously told Oprah.com she was "trying to go with" ageing.
"I think what ages a face most is disappointment and a lack of enjoyment. So I try to do what I love," she said.
The 12th season of Australia's Channel 7 cooking show follows a two-year hiatus for MKR, which suffered declining ratings in 2019 and 2020.
Presumably, in a bid to compete with its rival prime-time show, Channel 9's Married At First Sight, the series was copping criticism for overdoing it on the dramatics and straying from its humble roots.
In an effort to bolster the franchise, the network parted ways with original judge Evans following a slew of controversies, and promised the series would be bouncing back to its core values of "real food and real people" in 2022.
It's understood Lawson will only feature in half of the season, with former MasterChef judge Matt Preston joining Feildel for the back half. Celebrity chefs Colin Fassnidge and Curtis Stone are also set to return as guest judges.