Lean protein is a core part of your meal plan on the South Beach Diet and there's a good reason why: Lean protein allows you to maintain muscle mass while losing weight, which keeps your metabolism running at full speed. Cutting back on protein during weight loss, on the other hand, contributes to a loss of muscle mass and a slower metabolism. Lean protein is also an excellent choice when it comes to satisfying hunger and keeping blood sugar levels steady.

When it comes to protein, the best choices include lean cuts of beef (such as eye of round), ground beef (sirloin, lean, and extra-lean), tenderloin, top loin, and top round, as well as skinless turkey and chicken breast, pork loin and pork tenderloin, fish and shellfish, and soy-based meat alternatives that contain less than 6 grams of fat per 2- to 3-ounce serving. Protein sources that are high in saturated fat should be avoided. These include brisket, liver, rib steaks (like prime rib), chicken and turkey pieces with the skin (as well as dark meat), duck, and goose.