Lean protein is one of the best fat-burning sources of protein out there. Turkey is often overlooked next to the revered white boneless, skinless chicken breast, but it's actually even leaner. And don't be too worried about the belief that turkey breast makes you tired. Tryptophan isn't the only amino acid found in the lean poultry cut—the more obvious reason you're in a food coma post-Thanksgiving dinner is that you just had a big feast.