Belle Gibson, a Melbourne-based blogger and author, built a publishing empire on a preposterous premise: that she had contracted cancer from the H.P.V. vaccine. Later, she claimed, it spread to her brain, blood, spleen, and uterus. But after discovering the power of vegetables, her cancer went into remission, never to return as long as she kept eating her greens.

It was 2013—early days for our collective wellness obsession—when Gibson launched the Whole Pantry mobile app, a collection of vegan and gluten-free recipes that she claimed had helped her heal. She was already one of Instagram’s first breakout stars, vaguely Nordic-looking, more often than not captured in the produce aisle of the grocery store. The app, along with a cookbook published in 2014, was so successful that Apple wanted in: during the development of its Watch, the company decided Gibson’s app would be loaded onto the devices by default.