The Role of Protein in Your Diet

Whether you are active or not, protein is an essential macronutrient. Like carbohydrates protein contains 4 kilocalories per gram. Proteins main job is to build and repair muscle. Because of the job that protein has, we do not really want to use protein as an energy source. For protein to do it job, carbohydrate and fat intake needs to be met (for more on carbohydrates click here and for more on fats click here).

Types of Proteins

Amino acids are consider the “building blocks” of protein. There are 9 essential amino acids which have to be consumed through your diet. These include arginine, leucine, lysine, isoleucine, methionine, phenylalanine, threonine, tryptophan, and valine. There are also 11 non essential amino acids. These include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine. Protein sources that contain all 9 essential amino acids are called complete proteins and protein sources that are missing one or more of the 9 essential amino acids are called incomplete proteins. Examples of complete proteins include animal based protein sources like meats and cheese. While incomplete protein sources can be nuts and seeds.

Proteins Role in Exercise

Since the main job of protein is to build and repair muscle tissue it is not directly used during exercise like carbohydrates and fats are. However, if it needs to be used for energy it can be. Gluconeogenesis is the process that uses non carbohydrate sources for energy. For example, protein. For protein to be used as energy it gets broken down into amino acids and then converted to glucose through gluconeogenesis. Glucose then provides the muscles with energy. Once the amino acids are converted to glucose they cannot be converted back to amino acids so that protein does not get used to build and repair muscle tissue. See how important it is to make sure you have adequate amounts of carbohydrates and fats in your diet?

If the body has to constantly be using protein for energy it is not able to perform other its other functions (build and repair muscle, regenerate skin cells, etc.). During exercise your body is stressed which is going to cause cortisol to be released. Cortisol is going to trigger muscle protein breakdown. You can counterbalance this by consuming enough protein, carbohydrates, and fat. Without sufficient amounts protein breakdown is going to be happening more than protein synthesis. We want the opposite to happen. We want muscle protein synthesis to occur more than breakdown which will lead to increase muscle mass, strength, and endurance.

Your body also does not have protein readily available to use like it does carbohydrates and fats. So when the body needs protein it is going to take it from your skeletal muscles and your skin.

How Much Protein Should You Consume?

The RDA for protein is set at 0.8g/kg. However, this is the bare minimum and I would argue it is a very low bare minimum. There have been several new research studies showing that a higher protein intake (higher than the RDA) is beneficial. Studies have ranged from 0.8-4.4 g/kg. The really surprising and honestly really cool thing that the research studies of higher protein intake has shown is that the subjects with the higher protein intake (closer to 4.4g/kg) versus the subjects with lower protein intake (closer to 0.8g/kg) actually had limited fat gain even though the higher intake group was eating more calories than the lower. This is really where protein can show off some of its really cool “features.” When talking about metabolism there is something called the thermic effect of food (TEF). When we start the digest food our bodies burn calories while digesting. Carbohydrates have a TEF of 5-10%, fats 0-5%, and protein 20-30%. So it essentially “costs” more to digest protein than it does the other macronutrients. A higher protein intake is going to increase your TEF, resulting in an increase in your metabolic rate.

But what if you eat too much, wont you gain fat? So, this is another cool “feature” about protein. When you eat protein the first thing your body wants to do with it is use it for protein synthesis, then it wants to burn it for energy, and the last thing (assuming carbohydrate and protein needs are met) it wants to do it turn it in to glucose, and then fat. The above research studies that were mentioned has shown this effect. Higher protein = higher TEF=higher metabolic rate as well as higher protein intake is not going to automatically be stored as fat. Another cool “feature” about protein is it is going to keep you fuller longer. Add that in with some fiber and you are good to go.

So how much should you actually eat? For someone who is sedentary aim for about 1.2-1.8g/kg, if you are active aim for 1.4-2.0, if you are active and trying to build muscle aim for about 1.6-2.4g/kg, and if you are over weight with a goal of fat loss aim for 1.2-1.5k/kg. If you decide that fat loss is the goal whether you are sedentary or active keep your protein intake on the higher side. A calorie deficit is needed to lose fat so when you start that deficit cut the calories from carbohydrates and fat do not cut calories from protein. This is going to help save lean body mass (so will resistance training) as well as help with metabolic adaption. There is also something called muscle protein synthesis (MPS) that we need to pay attention to. This process helps repair muscle damage caused by exercising (yes exercising caused muscle damage). For this process to start it needs 20g of protein. Continually spiking MPS throughout the day with multiple meals with be more beneficial than just spiking it with one meal. Protein distribution is important, you do not want to eat 100g of protein in one meal and then little to no protein in others. You can do this by aiming to have at least 20g of protein per meal. Spiking MPS pre and post workout is also super important so make sure your meals around your workout have at least 20g of protein as well as some carbohydrates.