SlimFast Foods Co.’s owner is considering a sale of the weight-loss business, almost four years after the private equity firm bought it from Unilever Plc, people with knowledge of the matter said. Dallas-based Kainos Capital is working with investment bank Harris Williams to run an auction process for SlimFast, said the people, who asked not to be identified because they weren’t authorized to speak publicly. A sale is expected to value the company at about $400 million and is attracting interest from other buyout firms, the people said.