Out: 1/4 of your meat
In: Lentils
Why: Saturated fat (which meat tends to have a lot of) can gum up arteries and speed you toward heart disease. Too little fiber (meat has zero) can accelerate the aging of the gastrointestinal system. Beans and lentils are the opposite of meat: lots of fiber and no saturated fat—and they provide protein. How can you lose?

Out: Regular yogurt
In: Low-fat or fat-free yogurt
Why: Dairy foods are a great source of calcium and vitamin D, which help keep bones from thinning. But the saturated fat in whole milk, cheese, and yogurt contributes to artery clogging. Switching to low- or no-fat dairy gives you all the benefits without the risks.

Out: 1/4 of your meat
In: Fish
Why: Fish is an ideal lean protein source, low in saturated fat. Certain varieties such as salmon are also high in omega-3 fatty acids—vital for heart and possibly brain health. Unfortunately, some species also contain contaminants: If possible, eat wild versus farm-raised salmon and limit albacore (white) tuna to one meal a week. If you're pregnant or nursing, check out the guidelines at www.epa.gov/ost/fishadvice/advice.html.

Out: Bag of potato chips
In: Slices of apple
Why: An apple has no fat, few calories, lots of soluble fiber, and antioxidants. What does a potato chip offer? Pretty nil on the valuable nutrients score, and it's a great source of oil, calories, and salt. A good rule of thumb is to go with foods that come packaged by Mother Nature, i.e., apple (skin) versus chips (plastic bag), banana (peel) versus candy bar (wrapper). Both you and the environment will be around longer to enjoy each other.