Yes, you want to eat better. But a complete dietary overhaul seems like a full-time job -- one you just don't have the energy to take on. Instead, replace a few key items with healthier options, and focus on what you're adding to your diet -- not on what you're losing.

Baked, roasted, or mashed, sweet potatoes offer all the comfort-food satisfaction of white potatoes -- but with much more nutrition. One medium sweet potato delivers more than a day's worth of vitamin A (in the form of beta-carotene), plus 57 percent more fiber and 55 percent more vitamin C than white potatoes. Rich and moist, they taste great -- even without loads of butter or sour cream.

Like croutons, walnuts add heft and crunch to salads. But thanks to their protein, fiber, and fat, they also add long-lasting energy. Unique among nuts for their high amount of alphalinolenic acid, a type of omega-3 fat that protects against heart disease, walnuts also contain melatonin, which helps regulate sleep -- and they're a good source of phytosterols, which help lower cholesterol levels. Toast them lightly for added crispness.

Looking for something rich and creamy to spread on a sandwich? Try an avocado. Per tablespoon, this mild, buttery fruit has about half the fat of low-fat mayonnaise and half the calories. The luxurious texture of avocados comes from heart-friendly monosaturated fat. As a bonus, you get healthy amounts of fiber, folate, niacin, and vitamins B6 and K, too. Avocado pairs particularly well with turkey.

Mushrooms provide more nutrients than they generally get credit for, but shiitakes stand out for their combination of great flavor and medicinal value. Extensively studied in Asia, shiitakes contain lentinan, a type of carbohydrate that stimulates your immune system, helping to protect against (and fight) cancer. Another compound in shiitakes, eritadenine, lowers cholesterol. Shiitakes' savory taste works well in stir-fries, sauces, and gravies. Either discard the tough and fibrous stems, or save them to add an earthy flavor to a broth.

Dark chocolate gets its signature bitter flavor from flavonoids, heart-protecting antioxidants that milk chocolate contains in short supply (white chocolate has none). Studies have shown that including small amounts of dark chocolate in your diet can boost your health -- for example, it helps lower blood pressure. So go ahead and indulge a little in this rich-tasting treat. When buying a bar, be aware that most manufacturers don't list flavonoid contents on their labels. But cocoa percentage provides a clue -- the higher, the better. Try a dark chocolate that contains 70 percent or more cocoa.

You know that iceberg lettuce is no nutritional star, but you love its crunch in salads, sandwiches, and tacos. Next time you shop, reach for romaine lettuce instead. It has the same crisp texture as iceberg but more than three times the folate and seven times the vitamin A, as well as more potassium and vitamins C and K. Like other leafy greens, romaine is rich in carotenoids, which studies show may inhibit the growth of certain cancers.

With more fiber, calcium, vitamin E, and magnesium (not to mention flavor), almond butter makes a great alternative to cream cheese on bagels or breads. We confess: This switch does increase calories, but the protein gained mitigates the effect. How? High-protein foods add to satiety, and studies show that protein in a meal makes you feel more full -- so, ultimately, you eat less. You'll also be doing your heart a favor by replacing the high level of saturated fat in cream cheese with the mostly monounsaturated fat in almond butter. For a change of pace, try the crunchy version of this spread.

You can reduce your risk of diabetes, heart disease, stroke, and weight gain by eating more whole grains. A good rule of thumb is to make at least half your grains whole. 

For baking, keep a container of whole-wheat flour next to your all-purpose flour and use equal amounts of each.You'll get almost three times the fiber, as well as important antioxidants. 

Try the swap and see what you think; if you don't like the results, consider white whole-wheat flour, which offers the same benefits but is made from a milder-tasting variety of wheat.

Common vegetable oils such as corn, safflower, and sunflower are high in omega-6 polyunsaturated fats. While our good health depends on these fats, Americans tend to get more than we need, which can interfere with our bodies' ability to use omega-3 fats and lead to problems with inflammation. Instead, choose canola oil. It contains more omega-3s than other common cooking oils. Like olive oil, canola is high in cholesterol-lowering monounsaturated fats. Plus, its neutral flavor and 400-degree smoke point make it suitable for both baking and sauteing.

Plain whole-milk yogurt may sound like an indulgence, but compared with sour cream, it's downright spartan. Cup for cup, whole-milk yogurt has less than half the calories and one-third the total and saturated fat of reduced-fat sour cream, yet it boasts 16 percent more calcium. Use it in baked goods, dips, and as a garnish instead of sour cream. Stick with whole-milk versus low-fat or fat-free yogurt; you won't feel like you're sacrificing flavor for health. Just don't go overboard (think teaspoon, not ladle).