2014 - This summer LeBron James slimmed down, losing some 15 pounds to ready himself for the upcoming season. His secret? Cutting carbs. The approach is nothing new: Two years ago, Dr. Cate Shanahan helped the Los Angeles Lakers switch from high-carb to low-carb and become so-called fat-burners, meaning that their bodies burn fat as a primary fuel, instead of carbohydrate. It's a fast way to lose weight while keeping muscle, a move that can help prevent injuries and boost energy reserves for players — and everyone else.