Overall, Bazilian says she generally agrees that ketosis could help an elite athlete like LeBron with his energy levels, but it would require a lot of medical supervision. What's more, says Bazilian, the method is not good for endurance athletes like marathon runners, who require long-term use of carbs and fat to perform their best. Plus, there isn't much scientific research to back up claims that ketosis is effective. For all those reasons, it’s likely a bad idea for someone who is not a closely monitored professional athlete, she says.