The Ultimate Guide to Protein – The Most Talked-About Macronutrient

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Whether you’re embarking on a fitness journey or just trying to be more conscious of what you eat, protein is likely a key consideration in the kitchen. And if it’s not…maybe it should be. As a personal trainer and nutritionist, this is a topic that I am asked about often. And I am here to spill the….whey? (Sorry, I had to)

As you probably already know, protein is one of the three macronutrients, alongside fats and carbohydrates that our bodies need in order to function properly. However, protein usually receives a bit more hype and consideration than the other three. After all, proteins are the building blocks of living organisms and can be instrumental in building an optimal physique or just improving your overall health. Whether you have been counting your macros for years or are simply looking for a good place to start, this guide will cover everything you need to know about this macronutrient—from its role in your health to how much of it you actually need.

What is Protein?

Protein is the only major nitrogen-containing part of the diet and the macronutrient that your body uses to build and repair tissues and molecules. It’s essential for the growth and maintenance of muscle tissue, bones, skin, organs, nails, and hair.

Some examples of proteins in the human body include enzymes, hormones, muscle tissue, collagen, and blood cells—and because of its abundance in these vital compounds, protein is an essential contributor to nearly all bodily functions. While protein can be found in both plant and animal foods, it is more prominent in animal products like meat and dairy.

Like carbohydrates, protein contains 4 calories per gram. However, protein has a higher thermic effect than the other two macronutrients, meaning that your body burns more calories to digest it than it would with other nutrients, which can be viewed as an additional benefit for those trying to lose weight.

Healthy protein illustration, protein powder, dairy, legumes, vegetables and eggs

What are Amino Acids?

Just like proteins are the building blocks of the human body, amino acids are the building blocks of protein. Without getting into the biochemical details, amino acids are the molecules that combine together to form protein. When you eat dietary protein, your body breaks it down into its individual amino acids and then uses them to build tissues and molecules within the body or excrete them as waste. Amino acids can be categorized by their chemical structure but primarily are placed into two groups: essential/non essential, and glycogenic/ketogenic.

Glucogenic vs Ketogenic Amino Acids

Protein is not the preferred source of energy in the body, however, when consumed in a surplus, amino acids can be metabolized to ATP (the physiological energy currency). The difference between glucogenic and ketogenic amino acids is that glucogenic aminos can be used to create glucose where ketogenic aminos cannot. Instead, ketogenic aminos are converted into keto bodies which your body can use for energy in periods of low glucose availability or starvation. The only two true Ketogenic aminos are Leucine and Lysine. There are four others that are both glucogenic and ketogenic and the rest are glucogenic.

Essential vs Nonessential Amino Acids

There are 20 amino acids that our body uses to function, but there are only nine that humans cannot produce on their own. These nine amino acids are considered “essential” because must be obtained from the diet or through supplementation. The presence of amino acids in certain foods (along with their digestibility, absorption efficiency, and utilization) determines what is often referred to as protein quality.

Complete vs. Incomplete Proteins

When evaluating protein quality, we often group proteins into two categories: complete and incomplete. Incomplete proteins only have some of the essential amino acids while complete proteins have all nine. Animal products are complete proteins, while plant-based proteins are generally incomplete. Hemp and chia seeds, quinoa, and soy protein, however are exceptions (this also means that soy-derived plant products like tofu and tempeh are also complete proteins.)

While all nine essential aminos must be consumed through your diet in order to maintain healthy bodily function, they don’t necessarily need to be consumed together. So it’s important that vegetarians and vegans eat a balanced diet and consume complimentary proteins throughout the day (for instance, legumes and grains) to ensure they are obtaining all nine essential amino acids.

Special Amino Considerations

But not all complete proteins are treated equal, branched chain aminos, for example—and more specifically Leucine, has been shown to enhance muscle protein synthesis. For this reason, if your goal is to build or maintain muscle mass or reshape your body, a protein’s leucine content may be a consideration. Proteins that are high in Leucine include: whey supplements, casein supplements, milk, and soy.

How is Protein Digested?

The first step in protein digestion involves a process called denaturation which involves maintaining the protein structure but changing its shape. This process actually begins even by cooking the protein and cutting it into bite-sized pieces and chewing the food. However, most of the protein digestion occurs in the stomach following a series of hormones that trigger Hydrochloric acid and pepsin to begin breaking the protein into smaller peptide chains.

Those chains are then passed into the small intestine where additional enzymes break down the peptide chains even further until they become amino acids which are then absorbed and transferred to the liver. From this point, they will either be used for protein synthesis or excreted via urea.

While protein can be broken down for energy, it is not a preferred source so your body will metabolize carbohydrates and fat beforehand.

Protein digestion illustration, mouth chewing, enzyme breakdown in stomach, small intestine and liver

How Much Protein Do You Need?

How much protein you should eat in a day boils down to your goals, activity levels, and metabolic needs. The USDA recommends recommends a minimum of 0.8 grams of protein per gram of body weight for sedentary individuals. For those who engage in regular activity, they should aim to eat between 1.2 and 2.2 grams per kilograms of body weight—the more vigorous the activity level, the higher end of the spectrum. And regular resistance training is more taxing on your muscle tissues so a workout regiment that involves more of those exercises requires more intake.

Similarly, if you are on a weight loss diet and are therefore in a calorie deficit, you should increase your protein intake beyond that to better preserve muscle mass. No adverse effects have been demonstrated with an intake of up to 3.3 grams per kilogram of body weight.

How Much Protein For Muscle Growth?

For optimal muscle growth, individuals should eat between 1.2 to 2.2 grams of protein per kilogram of body weight. Notably, muscle protein synthesis only occurs when paired with resistance training. Therefore, protein alone will not increase muscle mass.

Protein timing is an important consideration when it comes to how much protein to eat with each meal. The average population does not need to concern themselves with protein timing so long as they are meeting the recommended daily allowance. However, research has found that that the most optimal way to eat protein for muscle synthesis is to equally distribute intake across 4 meals. The protein consumed must cross the threshold for an anabolic (muscle growth) signal to be sent, and this signal dissipates around 3 hours. For that reason, eating protein in comparable portions every 3 hours is optimal for muscle growth. In fact, studies have demonstrated an increase in muscle protein synthesis by as much as 25% using this method.

Optimal protein timing for hypertrophy or muscle growth diagram. 4 meals with 21 grams of protein every 4 hours

Protein Before or After Exercise?

While there have been proven performance and hypertrophy advantages to timing carbohydrates-heavy meals around a workout, the evidence around protein consumption around workouts is mixed. For instance a meta analysis of over 20 studies found minimal significance in protein timing and muscle hypertrophy. On the other hand, other studies suggest a slight benefit when protein is consumed one to two hours after resistance training.

All of this is to say that you shouldn’t be too concerned about timing protein around your workouts so long as you are hitting the recommended daily intake.

How to Eat More Protein

If you just realized you have to eat 180 grams of protein a day, you may be wondering how on earth you will do it without making yourself sick…the simple answer here is to make sure you are eating balanced meals evenly throughout the day. You are almost certainly going to be uncomfortable if you try to eat 70 grams at once (and at this point, it will be above what your body is physically able to utilize, so you won’t be receiving the same benefits) so the best way to avoid this is ensuring that all of your meals (and snacks) are protein rich throughout the day.

Protein shakes are a great way to make this a bit easier, whether its adding some to a morning smoothie or using it as an afternoon snack. I also suggest to my clients that they keep some easy high-protein snacks on hand. Some examples include: non-fat greek yogurt, low-fat cottage cheese, (non-deli) chicken or poultry, or healthy protein bars (like these RX bars).

Disclaimer: I am a certified nutrition coach and personal trainer, not a registered dietician or physician. The information in this post are meant to be for educational purposes only and should not be considered as medical advice. Please consult a licensed professional for specific dietary guidance

Common Questions

What Foods Are Highest in Protein?

Meat, fish and low-fat dairy generally contain the highest amounts of protein.

What is the Main Benefit of Protein

Protein fuels countless metabolic processes and is the building block of lean tissue and cells.


Mamerow MM, Mettler JA, English KL, Casperson SL, Arentson-Lantz E, Sheffield-Moore M, Layman DK, Paddon-Jones D. Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. J Nutr. 2014 Jun;144(6):876-80. doi: 10.3945/jn.113.185280. Epub 2014 Jan 29. PMID: 24477298; PMCID: PMC4018950.

Mero A. Leucine supplementation and intensive training. Sports Med. 1999 Jun;27(6):347-58. doi: 10.2165/00007256-199927060-00001. PMID: 10418071.

Schoenfeld BJ, Aragon AA, Krieger JW. The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. J Int Soc Sports Nutr. 2013 Dec 3;10(1):53. doi: 10.1186/1550-2783-10-53. PMID: 24299050; PMCID: PMC3879660.

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