Dark Chocolate A particularly sweet study found that daily consumption of roughly one and a half ounces of dark chocolate -- about the amount in a Hershey's bar -- reduced the stress hormone cortisol. (Stress has been linked to a sluggish metabolism.) Researchers suspect that certain compounds in chocolate, like caffeine and theobromine, may be responsible. Another reason to indulge: A study in the Archives of Internal Medicine found that adults who ate moderate amounts of chocolate regularly were actually thinner than those who didn't, even though they consumed more calories and exercised the same amount. Look for chocolate that contains at least 70 percent cocoa -- the darker, the better. Pair a square with a cappuccino for a midmorning pick-me-up or stir some chunks into homemade trail mix.
Eggs Eggs are the best protein source on the planet. They contain all nine essential amino acids, which your body needs to build muscle tissue. And the bigger your guns, the greater your fat-burning potential, because it takes more calories to maintain muscle than it does fat. Start your day with two scrambled eggs instead of waffles or cereal. Or get creative and cook an egg in an avocado for a dose of healthy fats: Slice the avocado in half lengthwise, remove the pit and carve out some additional space in the center, then crack an egg into it. Bake at 425° for about 10 minutes or until set, and voilà!
Sesame Seeds Animal studies showed that plant chemicals, called lignans, in sesame seeds enhance fat burning by increasing liver enzymes that break down fat. Many studies found that protein and essential fatty acids increase the metabolic rate, and sesame seeds are loaded with both. They're also a rich source of minerals and fiber. Roast sesame seeds (spread evenly on a baking sheet and put in an oven set to 325° for about 15 minutes or until golden brown and fragrant), then sprinkle them on salads, stir-fried vegetables, chicken, fish, and soups. Spread tahini (sesame paste) on celery or bread and opt for sesame seed buns and bagels over plain.
Smoothies Sipping a smoothie can stoke your fat-burning fires, as long as it contains whey protein powder. New research suggests that this substance triggers satiety hormones, including cholecystokinin, which sends your brain a "Hey, I'm full" signal. Plus, whey, a protein found in milk, contains the muscle-building amino acid leucine. When you're losing weight, eating whey protein can help reduce the loss of lean muscle mass, which keeps your metabolism revved. Whey protein powder isn't just for smoothies. Mix it into yogurt and pudding or add it to the dry ingredients when you're baking muffins or cookies.
Yellow Bell Peppers It's time to "pep" up your diet. About one-third of Americans are vitamin C deficient, and one yellow pepper supplies 341 milligrams, nearly three and a half times the amount in a large orange. The body needs vitamin C to produce a molecule called carnitine, which helps muscles use fat for energy and, in turn, boosts metabolism, people with higher levels of C in their blood had lower BMIs and less body fat, according to a study in the Journal of Nutrition. Raw yellow pepper strips make a satisfying snack with a little hummus, and they add crunch to fish tacos. Or core and clean a pepper and fill it with tuna salad (use low-fat Greek yogurt instead of mayo) for lunch.
Peanuts These fiber-packed nuts don't just help curb your intake of calories, they can help torch them too. "Peanuts induce a strong thermic response, which means that the process of digesting them actually burns calories. A study in the International Journal of Obesity and Related Metabolic Disorders found that when people consumed 500 calories worth of peanuts daily for 19 weeks, their resting metabolic rate increased by 11 percent, even without added exercise. Don't go overboard, as peanuts are calorie-dense. Keep a stash in your purse for a quick snack (aim for one ounce, or about two tablespoons, daily), revisit your childhood with an afternoon PB&J, or make pad thai with ground peanuts for a delish fat-burning dinner.
The Drink That Helps You Shrink Want to lose an extra 6.6 pounds a year? Down two glasses of water before breakfast (you can try it before any meal). People who did this in a recent study at Virginia Tech consumed an average of 75 fewer calories at their a.m. meal than those who didn't. The water acted as a calorie-free appetizer. It filled participants' stomachs, so they reported less hunger just prior to eating. Other research suggests that H2O boosts metabolism, because your body has to work to raise the temperature of the ingested water to match that of your core. In one study, people who drank eight to 12 glasses a day had higher metabolic rates than those who sipped just four.