Proteins 101

Protein is the direct precursor responsible for building muscle and encouraging recovery and repair. Further to that, protein is also an integrated part of connective tissue, immune bodies, hormones, cytoskeleton, enzymes and blood-clotting factors. Protein is made up of biochemical compounds consisting of one or more polypeptides typically folded into another structure to perform a specific function, especially when they are grouped together. A polypeptide is essentially a chain of amino acids (or “building blocks”) linked together by peptide bonds, which provide the nitrogen our muscle cells need for building muscle. Unfortunately, the body cannot produce all the amino acids that are needed to build protein. Termed the “essential” amino acids, these must be obtained from the food we eat. Through assimilation of amino acids, the body produces thousands of proteins!

The Muscle-Building Functions and Benefits of Protein

Consuming a diet high in protein is an absolute must when it comes to building a lean and muscular physique. Protein has many functions and benefits when it comes to bodybuilding, including increasing muscle mass; aiding in recovery, repair and preservation of lean muscle mass; regulating important processes and enzymes in the body related to metabolism; producing essential hormones; maintaining immune function and supporting storage and transport of important nutrients to the muscles. Below are some of the major functions that protein consumption can influence when it comes to bodybuilding.

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Growth Hormone and IGF-1

Protein consumption can increase two important regulators in muscle protein synthesis and metabolism: growth hormone (GH) and insulin-like growth factor 1 (IGF-1). GH stimulates calcium retention, strengthens and increases the mineralization of bone, increases muscle mass and induces protein synthesis, resulting in a positive nitrogen balance in the body. GH can also enhance the utilization and release of fat, stimulating breakdown and oxidation from fat cells, and increasing the amount of free fatty acids and glycerol in the blood that can essentially be utilized as fuel. Increased protein uptake can also stimulate the release of IGF-1, which is the primary protein involved in response of cells to growth hormone. IGF-1 is the key player in muscle growth, stimulating amino acid uptake and protein synthesis in muscle.

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Increased Fat Mobilization and Utilization

Protein consumption also increases plasma concentrations of the hormone glucagon. Glucagon is responsible for blocking the effects of insulin in adipose tissue. Increased glucagon leads to greater fat mobilization while at the same time decreasing the amounts and activities of the enzymes responsible for making and storing fat in adipose and liver cells. Studies have shown that with the lowering of these “fat enzymes”, there is greater fat loss during dieting activities and less fat storage when eating excess calories.

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Helps Maintain Insulin Levels

Consuming a mixed meal of protein and carbohydrates can result in a reduction of insulin release and maintenance of energy levels. Large concentrations of insulin in the bloodstream may activate fat-storage enzymes and promote the movement of triglycerides in the bloodstream into fat cells for storage, inhibiting enzymes that promote the breakdown of stored body fat.

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Thermal Effect of Protein

Protein has a thermic or metabolic effect, which means your body has to work harder to digest process and utilize it compared to other foods that are higher in fat or carbohydrate. Several studies have shown that repeated intake of high-protein meals have a greater thermic effect than meals of the same caloric value that were higher in carbohydrates or fats. The “thermal” effect of protein is one of the primary reasons that a higher protein diet is more effective for fat loss than a high-fat diet or a high-carbohydrate diet.

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Satiating Effect of Protein

Higher protein diets can sustain energy levels and cause a satiating effect. High-protein foods slow the movement of food from the stomach to the intestine. Slower stomach emptying means a delayed onset of hunger between meals.

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Amino Acids

There are hundreds of amino acids; however, only 20 are important for the human body. These 20 are the “standard amino acids” and are separated into “essential” and “non-essential” categories. The essential amino acids cannot be synthesized by the human body, but must be obtained from the food we eat, and include histidine, isoleucine, leucine, valine, lysine, methionine, phenylalanine, threonine and tryptophan. The non-essential amino acids are produced by the body within the liver, and include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine. These two groups of amino acids can aid in repair, growth and development of muscle tissue, improve concentration and attention, and help maintain immune function. Other biologically important roles for amino acids include fat transport within cells via carnitine, the disposal of excess nitrogen via ornithine, and synthesis of other molecules such as creatine, which drives energy generation for muscles, or even tryptophan, which is a precursor to the neurotransmitter serotonin responsible for mood and sleep.

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Branched-Chain Amino Acids

The most important amino acids for muscle building are the branched-chain amino acids (BCAAs), which are metabolized in the muscle. The BCAAs include leucine, isoleucine, and valine, which are all part of the essential amino acid group. BCAAs are a dietary necessity for bodybuilders. BCAAs not only play an important role in maintaining or preserving muscle tissue during exercise, but also promote muscle anabolism or protein synthesis via multiple pathways, help to reduce muscle catabolism, aid in muscle recovery and increase the production of other important amino acids such as glutamine. Studies show that BCAAs are important for muscle growth, recuperation, and for fighting fatigue. They can provide as much as 15 percent of your total energy during extended workouts. By ensuring adequate amount of BCAAs in your body, both before and after training, you can delay fatigue, guard against training-induced muscle breakdown and expedite recovery. Leucine is one of the most important because of its ability to directly stimulate muscle protein synthesis by activating a major complex in the anabolic pathway called mTOR. Research has shown that leucine has a positive effect on protein metabolism, increasing the rate of protein synthesis and decreasing the rate of protein degradation after intense training.

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Leucine, mTOR Activation and Muscle Protein Synthesis

Leucine is an important regulator in skeletal muscle protein synthesis after exercise. Whether you are an endurance athlete or bodybuilder, exercise causes muscle protein turnover. This is when the rate at which protein degradation or muscle breakdown increases and the rate at which skeletal muscle protein synthesis decreases, essentially resulting in catabolism of hard-earned muscle. In fact, leucine has about a tenfold greater impact on protein synthesis than any other amino acid. It has been shown that leucine activates a major complex in the anabolic pathway called the mammalian target of rapamycin, or mTOR. Think of mTOR as the amino acid sensor of the cell. mTOR is sensitive to leucine concentrations. Decreasing leucine concentrations signal to mTOR that there is not enough dietary protein present to synthesize new skeletal muscle protein, and it is deactivated. As leucine concentrations increase, it signals to mTOR that there is sufficient dietary protein to synthesize new skeletal muscle protein and mTOR is activated.

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Leucine Supplementation

Supplementing with leucine can reduce protein breakdown and increase protein synthesis. One study showed the effect of recovery drinks on skeletal muscle protein synthesis after a bout of resistance exercise. The drinks tested included carbohydrate-only, carbohydrate plus protein, and carbohydrate, protein and leucine. The researchers found that the mixture containing carbohydrate, protein and leucine had a greater impact on skeletal muscle protein synthesis than the carbohydrate-only and the carbohydrate plus protein drinks. This may be due to leucine providing a protein-sparing effect by decreasing the rate of protein breakdown and further stimulating protein synthesis. It has been shown that in order for protein balance to become positive after a workout, dietary protein, specifically the amino acid leucine, must be consumed and protein balance will remain negative until it is consumed. These results may be due to the rapid spike in plasma leucine that a free-form leucine supplement induces compared to whole proteins, which take long periods of time to be digested and utilized by the body. Thus, plasma levels increase slowly and plateau. Even with a fast digesting protein such as whey, it can take hours for the leucine in whey to be liberated from the protein and enter circulation; therefore, leucine concentrations in the plasma never spike to high levels. Supplements containing isolated leucine are quickly absorbed into circulation, spike plasma leucine levels and can increase intracellular leucine concentrations, activating the anabolic pathways involved in protein synthesis. FUSION’s AGENT•M powder offers up a substantial amount of leucine at 5.5 grams per serving and comes in two convenient formats that can be used before, after or even during your workouts to help kick-start muscle anabolism and minimize protein degradation.

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Protein Consumption and Meal Timing

To build muscle, it‘s essential that proper amounts of high-quality protein be consumed at the proper times. That may seem easy, as there are many sources of protein to choose from. However, not all protein is created equal! Some sources of protein are far superior and should be at the top of the list when it comes to bodybuilding. Nutrient timing of protein meals is even more crucial! Eating frequent, high-quality protein meals will keep the body in an anabolic state and ensure development of lean muscles. Meals should be between 1 and 1.5 grams of lean protein per pound of body weight, dependent on your activity level and muscle-building goals. For example if your weight is 185 pounds, you should be consuming 185 to 278 grams of protein, which equates to 31 to 46 grams of protein per meal divided out over six meals.

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Breakfast Protein

Upon waking, your first meal should be consumed within 30 minutes to kick-start the metabolism. During sleep, the body goes through a “fast,” utilizing the stored energy from the liver, fat cells and even our muscle cells to facilitate recovery; therefore, it‘s important to get the proper nutrients back into the body quickly. Whey isolate is a good source for this.

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Sustaining Positive Nitrogen Balance throughout the Day

After your first meal, meals should be consumed every 2.5 to 3 hours to maintain an active metabolism and sustain a steady source of amino acids to the muscles all day long. Frequent protein consumption is important because amino acids cannot be stored in the body like carbohydrates, and only a very small amount can remain in the bloodstream. Therefore, to maintain an anabolic environment, complete proteins must be eaten consistently, every few hours with every meal. Large increases in the amount of amino acids in the blood can cause protein synthesis rates to increase as well as decrease protein breakdown. Maintaining a positive nitrogen balance helps to prevent the body from utilizing its own muscle tissue to get the nutrients it needs to build muscle protein. Eating small, evenly spaced meals keeps insulin levels stable, a requirement for proper fat metabolism and proper growth. Eating frequently is also easier on the digestive system and more efficient. Studies have shown that eating frequent smaller meals will raise the metabolic rate, burn more calories and result in less body fat storage.

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Pre-, Intra- and Post-Workout Protein Timing

Protein timing is essential to maximize muscle building. Essential amino acids are critical to keeping blood amino levels high and to help maintain positive nitrogen balance before, after and even during training. For this reason, it’s optimal to supplement with a BCAA, whey protein isolate or a whey protein hydrolysate, which are easily digested and have a high absorption rate, to allow for quick transport and uptake by the muscles. Whey protein boasts the highest concentration of BCAAs versus all other proteins, and it’s also one of the most complete proteins in nature, providing the highest biological values of all proteins. After an intense workout, the body’s muscles experience breakdown, catabolism sets in and cortisol levels begin to increase. To shunt the catabolic process, your body needs the essential building blocks to rebuild muscle and increase anabolism or muscle growth. As previously mentioned, BCAAs can ignite protein synthesis, particularly after working out, when the body is craving energy to rebuild those muscles. Research has shown that the BCAA leucine has a positive effect on protein metabolism, increasing the rate of protein synthesis and decreasing the rate of protein degradation after intense training. Leucine does this by activating a major anabolic pathway that essentially turns on protein synthesis, switching on both growth hormone and insulin release! There is even some research to suggest that BCAA supplementation can also prevent decreases in testosterone levels caused by training. And if you want to create an even more favourable muscle-building environment, you need to add carbohydrates to the mix. Research has also shown that the combination of a carbohydrate with BCAA can not only work to quickly halt muscle breakdown, but also help stimulate muscle recovery and rebuilding faster than if just supplemented on its own. Two other great post-workout options related to the protein category are glutamine and creatine. Supplementing with glutamine after working out can reduce the amount of glutamine that is robbed from the muscles cells during training, resulting in muscle preservation and increased protein metabolism. Creatine works by providing muscle cells with the energy they need to perform more work through the generation of ATP, our muscles’ energy source. The result of supplementing with creatine is gains in muscle size and strength.

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Nighttime Recovery Protein

As discussed at the beginning of this section, during sleep the body goes through a “fast,” using up the nutrients in the bloodstream for recovery. To ensure nitrogen balance is maintained, protein consumption prior to bedtime should be considered. Slow-digesting protein, such as caseinate, supports immune function and muscle growth. Research conducted on casein protein has demonstrated it to sustain steady amino acid levels for up to seven hours after ingestion, making this protein an excellent choice as a nighttime protein, helping prevent muscle breakdown while sleeping.

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Protein Digestion

Proteins are classified into two groups based on their rate of digestion. The rate of digestion can have important effects on protein balance within the body. This balance between protein synthesis and protein breakdown determines muscle gain. Proteins can be divided into “complete” and “incomplete” proteins, as well as “fast” and “slow” digesting. Complete proteins contain the correct amounts of the essential amino acids needed by the body for muscle growth, while incomplete proteins are deficient in one or more of the essential amino acids. Deficiencies in the essential amino acids may suppress important metabolic functions necessary for repair and recovery of muscles. Fast-digesting proteins are those that get absorbed and utilized by the body quickly. Fast-digesting proteins can rapidly raise blood amino acid levels and create a quick and short-lived increase in protein synthesis, and therefore are often referred as “anabolic” proteins. Fast-digesting proteins include whey isolates, whey concentrates or any one of the protein hydrolysates. Slow-digesting proteins release amino acids into the blood at a slower, steady pace and can minimize waste, improve utilization, deter catabolism, and promote muscle synthesis. Slower protein food sources can include eggs, chicken, fish, dairy products and casein- or milk-based proteins. Proteins that enter the bloodstream slowly have a pronounced effect on protein breakdown, significantly inhibiting it even at low quantities. Both fast- and slow-digesting proteins offer significant benefits to athletes. Research has shown that proteins that enter the bloodstream rapidly significantly increase protein synthesis. Therefore, both types of protein should be used in strategic fashion, dependent on your immediate need.

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Protein and Biological Value

One indication of protein quality is its biological value (BV). All proteins have a BV attached to them. The BV is a score given to a protein in order to specify its absorption rate and bioavailability within the body and how efficiently the protein is used in the body. A high BV signifies that a large percentage of it is actual protein and that the protein can be absorbed and used easily, which also means it contains many of the essential amino acids our bodies require. At the time this system was introduced, eggs were given the highest number on the BV scale at 100 and all other proteins were compared to it. However, later it was found that isolated whey protein has a much higher BV, and dependent on the processing (hydrolyzed, concentrate, or isolate) used for extraction, this could also alter the BV anywhere from around 105 to 150 and above!

To determine a food’s BV, scientists provide a measured intake of protein and determine the nitrogen uptake versus the nitrogen excretion. A BV of 100 and above is considered maximal, whereby all of the protein absorbed has been utilized with none lost. There are some concerns regarding the accuracy of this evaluation system. BV tests are based on studies that measure protein utilization in a tightly controlled feeding environment and do not necessarily resemble real-life situations. For example, the tests are performed on food in their raw state, not as cooked or processed. Processing, cooking, portion size, vitamin and mineral intakes, can also change the amino acid profiles and reduce the BV. The BV index has a function and purpose, but should not be the only determining factor of protein selection.

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Biological Value of Various Protein Sources

Protein Biological Value (BV)
Whey 159
Whole egg 100
Egg white 88
Casein 80
Soy 74
Beef 80
Wheat Gluten 54
Cow’s milk 91
Fish 83
Beef 80
Chicken 79
Casein 77
Soy 74
Rice 59
Wheat 54
Beans 49
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Protein Sources

Protein from animal sources contains all of the essential amino acids that the body needs for recovery and protein synthesis. Good choices of meat protein include skinless, boneless poultry (chicken and turkey), and lean cuts of red meat such as round, chuck, sirloin or tenderloin. Besides being packed with protein, they’re good sources of B vitamins, iron and zinc. They also contain the important nutrient creatine, which can help drive energy levels in muscle cells.


Fish is a staple in the bodybuilding diet, especially when it comes to contest season. This very high-quality protein contains good-for-you fats found in the oils of fish, which offer great health benefits, including keeping the bad (LDL) cholesterol in check, and the good (HDL) cholesterol elevated. Stay away from scavenger species and shellfish, which have higher toxin levels. Stick to fin fish such as tuna, orange roughy, tilapia, cod, sole and salmon. Most fish fillets or steaks provide 22 grams of protein per 3.5-ounce serving, while a 6-ounce can of tuna provides 40 grams.

Red Meat

Red meat is high in iron and vitamin B12, which helps keep nerve and blood cells healthy. It also contains zinc, which not only is important to immune health but also is involved in maintenance of testosterone levels, as well as many other metabolic processes. For inclusion in a bodybuilding diet, stick to lean cuts including sirloin, tenderloin, or round eye. Generally, meats are labelled lean if they contain less than 10 grams of total fat per 3-ounce piece and approximately 22 grams of protein.


Two of the most popular choices for bodybuilding are turkey and chicken. With either option, it should be noted that the white meat, particularly the breast, is the choice source. Additionally, the meat should be eaten without skin, as this is primarily where the fat lies. Turkey is naturally low in fat, containing 1 gram of fat per ounce. A 5-ounce serving provides almost half of the recommended daily allowance of folic acid and is a good source of vitamins B1, B6, zinc and potassium. These nutrients have been found to keep blood cholesterol down; protect against birth defects, cancer and heart disease; aid in nerve function and growth; boost the immune system; regulate blood pressure and assist in healing processes. Chicken is considered a very good source of protein, providing 30 grams of protein per 3.5 ounces. It’s also a very good source of B3 (niacin) and B6, which help support energy metabolism of proteins, fats and carbohydrates into usable forms of energy. Niacin can also support regulation of blood sugar levels, helping to optimize insulin levels. Vitamin B6 is essential for the body’s processing of carbohydrate (sugar and starch), especially the breakdown of glycogen, the form in which sugar is stored in muscle cells and to a lesser extent in the liver. A 4-ounce serving of chicken supplies 72 percent of the daily value for niacin and 32 percent of the daily value for vitamin B6. Chicken is also a good source of selenium, which is an essential component of several major metabolic pathways, including thyroid hormone metabolism, antioxidant and immune function.

Dairy Proteins

Milk is considered a complete protein, and is a good addition to a whey protein shake. One cup of skim milk contains 8 grams of protein and just 90 calories. Milk is rich in all the essential nutrients that are vital for the health of our bones and teeth including vitamins, minerals, calcium, phosphorus, sodium, potassium, vitamin A, and the B vitamins thiamine, riboflavin and nicotinic acid.

Whey is the ultimate protein in terms of quality and bioavailability and contains the highest proportion of BCAAs, which are needed to build muscle tissue. Whey protein is extremely fast-digesting protein and highly soluble, making it great for after a workout to restore protein synthesis. In fact, studies have shown that whey protein can stimulate anabolism after working out. Whey protein can be used as a source of protein for a quick meal or can be added to almost any food to supplement your protein needs.

Casein is a rich and slow-digesting protein source that supports immune function and muscle growth. Research conducted on casein protein has demonstrated it to sustain steady amino acid levels for up to seven hours after ingestion, making this protein an excellent choice for preventing muscle breakdown.

Cottage cheese is unlike most other cheeses, which are strictly off the list when it comes to bodybuilding. Cottage cheese is very high in protein and low in calories. One-half cup of fat-free cottage cheese contains 15 grams of protein, and one-third cup of regular cottage cheese contains 9 grams of protein.

Yogurt is made from milk that has been cultured with bacteria. This dairy product has all the nutritive value of milk and is easier to digest and offers good-for-you bacteria such as acidophilus and lactobacillus, which are beneficial to your digestive system. They can help your body make important vitamins, principally vitamin K, as well as some of the B-complex vitamins. These good bacteria are important in fighting certain infections as well as in helping to maintain proper elimination. One cup of non-fat yogurt provides approximately 8 grams of protein per serving.

Eggs and egg whites are considered the perfect protein source and generally are used as the standard against which to measure the quality of all other protein sources. Eggs do contain cholesterol, but they also contain lecithin, which helps to prevent fats from accumulating on the walls of the arteries. They also contain approximately 13 essential vitamins and minerals, including folate and vitamin D. Whole eggs should be eaten in moderation, while egg whites are a great alternative packed with just protein. One half cup of egg whites provides 24 grams of protein and zero grams of fat!


Vegetable Proteins

Legumes may not be not a typical protein selection when it comes to bodybuilding but can provide many nutrients, including protein, complex carbs, B vitamins, iron, phytochemicals, potassium, magnesium and calcium, and are a good meat alternative. This vegetable class includes beans, peas and lentils. Generally speaking, legumes provide between 7 to 10 grams of protein per half cup, are low in fat, are high in fiber and contain no cholesterol. It should be noted that, with the exception of soy, this source of protein is not considered complete, which means that legumes do not contain all the essential amino acids needed, and therefore are not a preferred source of protein for bodybuilders. Additionally, bodybuilders and athletes have unique needs and increased metabolic requirements for amino acids such as tyrosine, methionine, lysine and carnitine, which serve as building blocks for stress hormones and energy compounds; these specific aminos are often deficient in certain legumes. There are some ways to balance out the amino acid profile. Combining two incomplete sources of vegetable protein such as rice and beans can provide you with the full complement of essential amino acids.

Soy is a great protein alternative to animal choices and even great for those who have allergies to lactose. Soy protein contains saponins, which have been shown to support healthy immune system function, and isoflavones, which have been shown to help maintain good cholesterol levels and reduce bad cholesterol levels. This derivative of soy has also been shown to improve bone retention. Soy protein is also low in fat and contains other healthy compounds such as phytates that can act as antioxidants. Protein powder made from ground, roasted soybean can deliver all the benefits soy has to offer.

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Protein Sources and Amount of Protein per Serving

Protein Source Serving Size Grams of Protein
Beef, Sirloin, Grilled 6 oz 51 g
Beans, Kidney 1 cup 7.5 g
Cottage Cheese, 1% 1 cup 28 g
Chicken Breast, Boneless, Skinless 6 oz. 40 g
Fish, Salmon 6 oz. 44 g
Fish, Tuna 6 oz. 42 g
Milk, 1% 1 cup 8 g
Yogurt, low-fat 8 oz. 12 g
Tofu 1 cup 20 g
Turkey 6 oz. 42 g
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