For many, eating chicken, beef, eggs, cheese, and soy is all the same. After all they are all protein-rich food sources. Yes, but just as fats and carbohydrates have gone through a further classification—making some options better than others—not all protein food sources are created equal to build strong muscles and maximize a lean body mass.

“Protein allows for greater satiety, helps maintain lean muscle mass—benefiting your metabolism—and has the highest thermogenic affect of the macronutrients (i.e., protein, carbs, and fat), meaning protein requires the most energy for the body to break it down,” says Corinne Dobbas, MS, RD, registered dietitian for Western Athletic Clubs.

Several studies have shown that diets higher in this macronutrient allow more fat loss than diets with a lower protein intake. Recently, another study found that when eating the same calories from protein or carbohydrates for breakfast, the protein eaters better controlled their appetite during the day.

 Eggs and Nuts Essentials

Protein intake has a stellar role in any diet, in which the ultimate goal is to lose weight, preserve body mass, and improve lean body mass ratio.

Studies show that to enhance muscle protein and support fat loss, a protein serving should hold at least 10 g of essential amino acids per serving.

Proteins are made up of many amino acids. “There are 20 amino acids that form the building block of protein,” says Dobbas. “Some of these the body can make it—known as non-essential amino acids— while others it can’t—essential amino-acids.”

Yogurt, chicken, and eggs are “complete” protein because they provide all the nine essential amino-acids, but other sources like beans, rice, nuts miss some of these amino-acids, which make them an “incomplete” protein.

Exercise Protein Enhancement

Why does complete and incomplete protein matter? You workout and watch what you eat, yet you still don’t see results. Sure you eat protein, but if you miss the complete protein sources—particularly the food that provides what it’s called the branched chain amino acids (BCAAs): leucine, iso-leucine and valine—your efforts may be lost.

“BCAAs, are taken up directly by the muscles without having to be metabolized by the liver first. They can help protect the muscles from getting broken down during exercise and to help repair and build muscle after exercise,” says Carrie Wissemeier, RD with BistroMD.

And more muscle means a greater caloric expenditure even at rest.

It’s not just the protein type that is important, but also when it is consumed.

In a recent study, when subjects ingested a mix of essential amino acids with sucrose after exercising, they showed significant amino acid delivery to the leg muscles, and overall muscle protein synthesis than when they had the same mix, after a sedentary period. In other words, for protein to be effective, you need to consume it along with exercise and not just by itself.

Beyond Dairy

Overwhelmed with all this protein rules? Don’t be. If you regularly eat milk, yogurt, and ricotta cheese you are providing your muscles with two of the most important proteins: whey and casein. “Whey is digested and absorbed faster than casein and is rich in BCAAs, however casein supplies a longer-lasting source of amino-acid, which is also important in the muscle-building process,” says Wissemeier.

But your protein options are not limited to dairy. Dobbas says other top BCAAs food sources include eggs, tuna, chicken, edamame, and quinoa.

From all three BCAAs, studies show that leucine seems to be the most powerful to maintain your muscles. Add more beef (lean cuts), lentils, chickpeas, peanuts, chicken, and soybeans to your diet.

Be careful to not overstuff your diet with protein. Wissemeier says that if you eat a lot of protein, but skip good choices of healthy carbohydrates, you will decrease energy and stamina, which will affect your performance.

“It is also important to remember that a diet high in protein can easily become a diet that is also high in fat,” adds Wissemeier. “Your body can only process 4 to 6 ounces of protein at one time, and the rest will be converted to carbohydrate and then stored as fat.”