CHICKEN
>> Why it belongs in your cart: The bird is particularly rich in the amino acid leucine. Preliminary evidence reported in the August 2006 European Journal of Applied Physiology suggests that leucine supplements enhance athletic performance by helping to facilitate efficient protein synthesis in athletes. Chicken is also a low-fat source of high-quality protein that boasts a number of vitamins and minerals which contribute to peak energy levels.

>> Choose the best: Fresh chicken should be in clean packages that are sealed tight and cold, while frozen chicken should be rock-solid to the touch. Look for products with no more than 7 grams of fat in a 3- ounce serving.

>> Make-ahead meals: Roast a small whole chicken when you have a few hours at home, then feast on it for several days: once when it comes out of the oven, then as part of soft tortilla wraps made with reducedfat cheese and chopped vegetables, and again as chicken salad made with chopped grapes or minced celery and fat-free plain yogurt.

PORK TENDERLOIN
>> Why it belongs in your cart: With its juicy, flavorful texture, you'd think pork tenderloin was full of fat. On the contrary, it contains about the same amount of fat as a boneless, skinless chicken breast, according to recently released numbers by the United States Department of Agriculture (USDA). It's also a stellar source of niacin, one of the eight B vitamins that help break down the carbohydrates, fats and protein in food and convert it to energy your body can use. Niacin is also involved in maintaining the health of your nervous system.

>> Choose the best: There's very little waste when it comes to pork tenderloin, so choose a package according to the number of people eating. Figure about 4—6 ounces per person. Sealed packages of tenderloin may be kept in the refrigerator for up to four days before cooking. Keep it longer by storing in the freezer for up to six months—just make sure each piece of meat is well wrapped in specially coated freezer paper (place the waxed side against the meat) or heavy-duty aluminum foil, polyethylene film or a zip-top plastic freezer bag.

>> Make it a staple: Slice a tenderloin crosswise into medallions, sauté in a bit of olive oil and serve over a whole grain such as brown rice. Pork tenderloin is at its best when prepared with an added spice rub or a flavor-packed sauce, or when it's marinated in the refrigerator for 30 minutes before cooking.

95%-LEAN GROUND BEEF
>> Why it belongs in your cart: Don't reach for just any type of ground beef—there's a big difference in nutritional value. A serving of 95%- lean ground beef (about 3 ounces) serves up an additional 6 grams of protein (21 grams total) and saves 150 calories and 9 grams of fat over its fattier counterpart, 75%-lean ground beef. Like other meats (and eggs), beef boasts high-quality protein, which means it provides all the amino acids you need to maintain and build muscle. A 2005 Journal of Nutrition study found that diets rich in high-quality protein make weight control easier for active women by helping them retain muscle while shedding fat.

>> Choose the best: Shop for meat last to keep it cool longer, and take it home immediately to store in the refrigerator or freezer. Choose ground-beef packages that are cold and tightly wrapped. Unlike other cuts of fresh beef, the surface of ground beef is generally reddishbrown because it's exposed to air during processing. As with any meat, defrost frozen ground beef only in the refrigerator—do not leave it out on the counter. When you use the microwave for defrosting, cook beef immediately.

YOGURT
>> Why it belongs in your cart: Yogurt contains protein, but its stellar calcium content is why it's worth eating. Calcium may help women stay slim as long as they continue to exercise and eat a balanced diet. The most convincing explanation for how calcium might exert its slimming effects is that a low calcium intake is known to increase the concentration of calcium within cells, thus signaling to the body that it needs more fat. This, in turn, inhibits fat breakdown. In addition to protein and calcium, yogurt supplies live active cultures to enhance digestive health and immunity.

>> Choose the best: Go for plain low-fat or fat-free yogurt. Choose a brand with live active cultures that provides no more than 120 calories and 2 grams of fat per cup and supplies 40% of the daily value for calcium (400 mg) and 2 grams of fiber.

>> Make it your go-to condiment: Serve yogurt over fruit salad, use it as the base for vegetable and fruit dips, prepare smoothies with it, stir into whole-grain cereal, or top a baked potato with yogurt and herbs.