Consistency is the most important factor in achieving your ideal physique. In the gym, it's about finding a program that delivers the results you want, then having the discipline to stick with it to the end. In your diet, it's all about getting enough protein, controlling the amount and type of carbs you consume, and avoiding things like refined sugars and artificial ingredients.

But there's no reason to feel confined to a world of chicken breasts and brown rice. Among the best muscle-building foods are some you may never have heard of, and others you may simply have overlooked, unaware of their anabolic powers.

Here are 15 of the most unlikely muscle-building foods: Get your grocery list handy and prepare to add some variety to your diet en route to bigger gains.

1. Mackerel

Mackerel comes from the same family as tuna but has a higher omega-3 content, which helps limit the chronic inflammation generated by intense hypertrophy-based training. Mackerel contains a variety of other nutrients, including large amounts of zinc, which is essential for maintaining testosterone levels.

A 2011 study found that adding zinc to the diet of hard-training athletes increased testosterone levels following exhaustive exercise. And a 2007 study on the hormonal effects of extra zinc found that it can also prevent the decrease of thyroid hormones that results from intense resistance training.

2. Beets

The nitrates found naturally in beets increase vasodilation and improve performance. A recent study published in the Journal of the Academy of Nutrition and Dietetics found that eating two medium-sized beets an hour and fifteen minutes prior to exercise improved performance, reduced the perceived level of exertion, and decreased the amount of oxygen that subjects' bodies needed to complete a workout.

This "rewiring" of the muscular mitochondria opens the door for you to force your body to do more work than it would normally be able to, allowing you to elicit a greater growth stimulus from intense, hypertrophy-based resistance training.

3. Greek Yogurt

Greek yogurt is produced in part by straining excess liquid and carbohydrates from regular yogurt; the resulting concentrated product has twice the protein. Just check the ingredient list before you buy, though, as some companies like to cut corners by adding thickeners and gelling agents, such as pectin, in an effort to give inferior products that classic Greek yogurt taste and texture. The straining process used to create Greek yogurt results in a higher concentration of casein, a slower-digesting milk protein that provides the body with a steady increase in blood amino-acid levels.

A 2012 study published in Medicine and Science in Sports & Exercise showed that consuming casein before going to sleep provided an increase in blood amino-acid levels that was sustained throughout the night and yielded a 22% increase in protein synthesis. Depending on your calorie needs, you can use full- or reduced-fat Greek yogurt as part of your muscle-building efforts—but always reach for the plain version and avoid those with added fruit and sugar.

4. Sardines

Tuna is popular for good reason, but when it comes to raw, muscle-building power, sardines are even better. Like tuna, sardines come canned and ready to eat; however, unlike tuna, which is most often packed in water or the less-than-appealing vegetable oil, sardines can be easily found in high-quality extra-virgin olive oil.

Sardines also have 27 times less mercury than you'd find in canned albacore tuna. Moreover, four ounces of sardines pack 1.8 grams of omega-3 fats, while the same amount of canned tuna contains just 0.3 grams. Omega-3 fats, mostly known for their beneficial effects on heart health, also have anti-inflammatory properties and can help fight inflammation and joint pain associated with heavy, high-volume training.

More important is their function in making leucine, an amino acid, more effective in its role as the catalyst for protein synthesis. Some research also suggests that omega-3 fats can actually help older people overcome agerelated deficits in anabolism, making omega-3s especially important for older lifters.

5. Kimchi

The ability of kimchi, a traditional Korean dish consisting most commonly of fermented napa cabbage, onions, garlic, and spices, to improve your body composition has less to do with its scant calories than the way in which it affects other food you consume. Because kimchi is fermented, it contains beneficial bacteria that help with digestion and nutrient absorption.

A 2011 study published in Nutrition Research found that adding kimchi to subjects' diets for four weeks decreased waist size and body fat percentage while improving blood-sugar control. This makes kimchi a potential ally in warding off excessive fat gain during your mass-building cycles.

The easiest way to include kimchi in your diet is to simply have it as a side dish with your meals. While you can find kimchi in the international section of most grocery stores, buy it from your local Asian market whenever possible—your dollar will go a lot further, allowing you to make kimchi a consistent part of your diet.

6. Chocolate Milk

When you're out of protein powder, chocolate milk is your next best option after workouts. Chocolate milk naturally contains a blend of both fast- (whey) and slow-digesting (casein) proteins. The added sugars in the chocolate boost the total carbohydrate content of the drink, giving you more muscle-building calories and recovery-boosting carbs.

Studies show that, compared with a traditional sports drink containing carbohydrates and electrolytes, chocolate milk is superior at resynthesizing muscle glycogen; stopping muscle breakdown through multiple channels; and kicking muscle growth into action by supporting muscle-protein synthesis at the molecular level.

One additional anabolic advantage that chocolate milk holds over other post-workout drinks is the presence of antioxidants in cocoa that can help reduce the oxidative, stress-induced muscle damage that occurs after intense training, especially workouts that emphasize forced reps and negatives.

7. Almonds

Almonds contain more protein and fiber than most nuts you'll find at the supermarket: One shot glass full of almonds contains 160 calories and 6 grams of protein. Almonds are also high in a naturally occurring type of vitamin E: alpha tocopherol, which is a more effective free-radical scavenger than the synthetic version found in most supplements.

They also contain high levels of B vitamins—essential for energy metabolism—making them the perfect adjunct to any mass-gaining diet; research from City of Hope National Medical Center suggests that using almonds to increase calories over carbohydrates will yield better improvements in body composition.

8. Vinegar

Shuttling nutrients toward your muscles and away from your fat cells is a key factor in developing a lean, muscular physique. Vinegar can help you do that. Animal studies show that the addition of vinegar to a high-carb meal causes more of those carbohydrates to be stored as muscle glycogen. The vinegar seems to act as a nutritional "trail guide," shuttling carbs to your muscles, to be used for recovery and for fueling your next workout.

This effect appears to be more pronounced with faster-acting, more dense carb sources, like potatoes. In order to elicit the nutrient-partitioning effects of vinegar, you don't need much: Studies in humans show that the beneficial effects of vinegar on metabolism start to appear after just a two-teaspoon dose.

Vinegar is the perfect addition to any salad, and goes well on green beans. Add vinegar to your first post-workout meal to maximize its glycogen-replenishing effects, then again at your last high-carb meal of the day so you'll benefit from the extra calories while still controlling insulin levels and the release of glucose into your body.

9. Avocado

While avocados were once withheld from muscle-building diets due to their high fat content, we now know that they provide a unique combination of nutrients that makes them a near-perfect lean-mass builder. The average avocado contains 20 different essential nutrients, 250 calories, 10 grams of fiber, and 15 grams of monounsaturated fat.

Research shows that substituting monounsaturated fat for saturated fat can shift fat gain away from the midsection. This will help keep your core looking and feeling tight during a mass phase, even if you gain some fat. Avocados can also improve the absorption of antioxidants known as carotenoids up to 15 times. Carotenoids are important nutrients for cell growth as well as for supporting a healthy immune system.

Avocados are best eaten when they're slightly soft to the touch. If your avocado is ripening too fast, just put it in the refrigerator (if it's been cut open, drizzle the flesh with some lemon juice first) to stop the ripening process. Avocado can be eaten sliced in an omelet, mashed with salsa as guacamole, or with a spoon right out of the shell.

10. Pea Protein

Whey and casein protein powders are popular because of their convenience, but also because of their high levels of essential and branched-chain amino acids. However, overuse of these proteins can actually lead to the development of a low-grade allergic response, so it's good to switch up your supplemental protein source every so often.

Pea protein is highly digestible and, unlike many other vegetarian protein sources, does not contain any "anti-nutrients" that inhibit the absorption and digestion of other nutrients. In addition, pea protein contains all the essential amino acids, including high levels of branched-chain amino acids and glutamine, making it a true muscle-building powerhouse.

11. Raspberries

Raspberries play several roles in building muscle. They improve digestive health so that the body is better able to extract all the nutrients from the food you're eating.

They also contain the most fiber of any berry, packing up to 8 grams per cup. Maintaining a high-fiber diet as part of your hypertrophy plan is important—it "works out" your intestines, ensuring they are toned and in top shape.

The rich, red color of raspberries is indicative of the high content of anthocyanin antioxidants. Research shows that antioxidants, like the anthocyanins found in raspberries, can boost your brain's sensitivity to leptin, an important hormone responsible for regulating your metabolic rate and insulin sensitivity.

12. Kefir

Kefir is a cultured dairy product produced through the fermentation of the lactose found in completely lactose free, making it a viable beverage for people with lactose intolerance. Kefir also contains a unique mixture of probiotics and bioactive peptides that allow it to produce additional muscle-building benefits beyond those elicited by the 14 grams of high-quality protein found in each cup.

The bioactive protein peptides found in fermented milk products like kefir have been shown to stimulate the immune system and immunoglobulin production. This is important, as it can help counteract the stress that frequent, high-volume hypertrophy training puts on your immune system, allowing you to continue training hard and growing big.

Research published in July 2012 also shows that kefir can block the genetic signals that jumpstart fat-cell growth, providing you additional support for your efforts to stay lean while still getting big. Bonus: the probiotics in kefir will help keep your digestive tract running optimally by boxing out bad bacteria and supporting the breakdown of all the food and nutrients you need to feed your body in order to make it grow.

13. Lentils

Lentils are a triple threat. They're packed with fiber, protein, and low-impact, slow-digesting carbohydrates. One cup of cooked lentils contains 230 calories, 18 grams of protein, and 16 grams of fiber. Lentils come in three main varieties—brown, green, and red. Each has a slightly different flavor; but if you're in a pinch and need food fast, reach for red lentils, which cook up in about 15 minutes, compared with 30 or 45 minutes for other types.

For a quick and easy muscle meal, try a traditional Middle Eastern dish called mujaddara—a combination of one cup of lentils, a cup of brown rice, and one caramelized onion.

14. Broccoli

High-volume, low-calorie foods like broccoliand cabbage are typically withheld from muscle-building diets as they can cause the early onset of satiety and fullness, which makes hitting a high-calorie target harder. But withholding broccoli and other vegetables that are members of the cruciferous family is a mistake, because they provide a hormonal advantage by reducing estrogen.

These kinds of vegetables, especially broccoli, contain several unique antioxidants and compounds that can help to improve your health in a variety of different ways, not limited to fighting cancer. Indole-3-carbinol and D-glucaric acid are two other nutrients found in cruciferous vegetables that aid in clearing excessive estrogen and toxins from your body.

These compounds not only play a role in the binding and clearing of naturally occurring estrogen, they can also bind xenoestrogens—synthetic compounds that mimic estrogen. Indole-3- carbinol in particular can interact with the genes responsible for putting together estrogen receptors by either blocking their action or decreasing their effectiveness.

The combination of these two unique compounds in broccoli works to clear excess and chemically similar estrogens while also impacting the ability of estrogen to work on target tissues. This allows you to minimize the negative effects of estrogen on your muscle-building goals. If you're still worried about the satiating effects of broccoli, roast or steam it; this will remove some of the intra-vegetable water content, making it easier to eat and less filling.

15. Quinoa

Brown rice is the traditional go-to carbohydrate for muscle-building diets, but quinoa, a grain that was once a nutritional staple of Peruvian Incas, provides several distinct advantages, both nutritionally and practically, over other classic carbs.

The unique nutritional characteristics of quinoa may be due in part to the fact that it isn't a grain, like rice; instead, the quinoa plant, whose seeds are harvested and eaten, more closely resembles spinach. One cup of quinoa contains 222 calories, 8 grams of protein, more zinc and magnesium than brown rice, and almost twice the fiber.

But where quinoa really sets itself apart as a top-notch muscle-building food is in its amino-acid profile and its place on the glycemic index: The glycemic index value of quinoa is only 53. This means you get a slower burn from the carbs in quinoa, giving you a sustained infusion of calories—and therefore energy—following your meal. Unlike the other carbohydrates in your diet, quinoa contains all the essential amino acids.

From a practical standpoint, quinoa also wins: It cooks up in just 15 minutes, which is three times faster than brown rice. To prepare quinoa, use two parts water or chicken stock to one part quinoa. It can be eaten as a hot side dish with your protein of choice, or mixed in cold as the base of a muscle-building salad.