Losing weight and feeling tired all the time

A superfood is easy to find in the grocery store, contains nutrients that are known to enhance longevity and has other health benefits that are backed by peer-reviewed, scientific studies. Broccoli makes the list because it's one of nature's most nutrient-dense foods, with only 30 calories per cup. That means you get a ton of hunger-curbing fiber and polyphenols -- antioxidants that detoxify cell-damaging chemicals in your body -- with each serving.

Apples have fewer than 50 calories but are a great source of antioxidants, fiber, vitamin C and potassium, according to SuperFoodsRx.com.

Blueberries are often singled out as a superfood because studies have shown they aid in everything from fighting cancer to lowering cholesterol. But all berries, including raspberries, strawberries and blackberries, contain antioxidants and phytonutrients. Worried about the price of fresh fruit? Experts say frozen berries are just as "super."

Salmon provides a high dose of omega-3 fatty acids, which studies show significantly lower the risk of heart disease. Omega-3 fatty acids fight back by reducing inflammation and slowing the rate of plaque buildup in blood vessels. Salmon is also a good source of lean protein.

Eating a breakfast high in protein is a good way to keep hunger at bay throughout the day. Eggs are full of choline, a nutrient that helps block fat from being absorbed in the liver. Choline may also help in preventing memory loss.

Many dieters shy away from nuts because of their high calorie and fat count. But studies show that eating a handful several times a week can help shed pounds and prevent heart disease. Almonds, in particular, contain lots of monounsaturated fats and fiber. (Healthy swap: Replace peanut butter with almond butter.)

Staying hydrated will keep you from munching absentmindedly, and if you choose to drink green tea, you'll also be increasing your metabolism, which will burn more fat. Plus, the antioxidants (yes, those again) found in green tea can help prevent cancer.

Quinoa is the popular whole-grain du jour because it also contains a good dose of protein to help build muscle. Yet including any type of whole grain in your diet -- from barley to brown rice -- will aid in weight loss by filling you up for fewer calories.

Beans, beans, the magical fruit; the more you eat, the more ... you lose weight. Black, kidney, white and garbanzo beans (also known as chickpeas) all end up on superfood lists because of their fiber and protein. They fill you up and provide muscle-building material without any of the fat that meat can add to your meal.

Spinach is a great source of iron, which is a key component in red blood cells that fuel our muscles with oxygen for energy. But researchers in Sweden recently identified another way in which these greens might keep you charged: Compounds found in spinach actually increase the efficiency of our mitochondria, the energy-producing factories inside our cells. That means eating a cup of cooked spinach a day may give you more lasting power on the elliptical machine (or in your daily sprint to catch the bus).

Walnuts are packed with tryptophan, an amino acid your body needs to create the feel-great chemical serotonin. (In fact, Spanish researchers found that walnut eaters have higher levels of this natural mood-regulator.) Another perk: "They're digested slowly," says Dr. David Katz, director of the Yale Prevention Research Center. "This contributes to mood stability and can help you tolerate stress."

Asparagus is one of the best veggie sources of folate, a B vitamin that could help keep you out of a mental slump. "Folate is important for the synthesis of the neurotransmitters dopamine, serotonin and norepinephrine," says Dr. David Mischoulon, associate professor of psychiatry at Harvard Medical School. All of these are crucial for mood.

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