Understanding Protein for Fitness and Athletic Training

Protein is an essential nutrient in our diet and is involved in numerous physiological processes. Understanding the complexities of protein is critical for improving sports performance and recovery.

Woman resting next to kettlebell and bottle
Woman resting next to kettlebell and bottle

Understanding Protein for Fitness and Athletic Training

7 minute read

What is protein?

Protein is an essential nutrient in our diet and is involved in numerous physiological processes. Understanding the complexities of protein is critical for improving sports performance and recovery. In this article, we will look at the fundamentals of protein, including its functions, sources, requirements, and importance in the diet of athletes seeking athletic goals.

Proteins are amino acid-based macronutrients that are commonly referred to as the “building blocks of life.” There are 20 amino acids, 11 of which are non-essential and 9 of which are essential. This means the body cannot synthesise them and must receive them through diet. Athletes have increased protein requirements compared to sedentary individuals, to meet the demands of muscle repair, growth, and metabolic function.

How protein powers the body

Muscle building and repair – Proteins serve as the building blocks for muscle, aiding in their growth and repair post-exercise. Protein is also essential for the synthesis of new muscle tissue, especially after resistance or strength training.

Enzyme function – Proteins act as catalysts for various biochemical reactions in the body, aiding in processes such as digestion and metabolism. Without enzymes, vital physiological functions would be compromised.

Immune system support – Antibodies are components of our immune system and are made of proteins.

Hormonal balance – Hormones, which are essential for regulation and coordination of various body functions, often consist of proteins.

Satiety – High protein intakes and protein-rich foods promote a feeling of fullness, which can aid in weight management by reducing calorie intake.

In summary, proteins play multifaceted roles, making them indispensable for both health and exercise performance. It is also important to underline that proteins play a role in successful ageing, so it’s not only young and fit individuals that need to focus on protein intake.

Protein requirements for athletes

Athletes’ appropriate protein intake is determined by several factors, including training volume, intensity, and specific goals.  It is widely acknowledged that athletes should consume greater amounts of protein than the current recommended daily allowance (RDA) of 0.8g/kg body weight (bodyweight)/day (>1-2.2g/kg body weight/day). There is currently little evidence that these higher protein intakes are detrimental to health in otherwise healthy persons, even though some of these guidelines can be up to twice as much as the RDA.

Only a handful of studies have looked at the protein needs of elite endurance athletes. In a policy paper on protein requirements for athletes, the International Society of Sports Nutrition (ISSN) states that athletes who perform strength training should consume 1.4–2 grams of protein per kilogram of body weight each day. Athletes with recreational or moderate training needs may require lower levels. For athletes engaged in endurance sports, an intake of 1-1.8g/kg of body weight is advised and elite competitors should consume more. Diets rich in protein don’t really help endurance athletes perform better; it would be wiser to zero in on consuming substantial quantities of carbohydrates to fuel performance.

Acute resistance training elevates the rates of muscle protein synthesis and breakdown. It additionally leads to stress and trauma, which necessitates higher protein availability for the body to heal. Compared to sedentary people, strength or power athletes may require a higher intake of protein in their diet.

While consuming more protein is often thought to be advantageous when an athlete wants to grow muscle, it is also essential when the athlete wants to lose body fat. When in an energy deficit, strategies that raise daily protein intake to 1.6–2.4g/kg body weight/day are more effective in maintaining lean mass than lower intakes. Because protein is both satiating and thermogenic, some athletes may also want to use it as leverage in a low-calorie diet when trying to shed fat mass.

Training and nutrition programmes that focus on reducing body fat and building muscle simultaneously are referred to as ‘recomposition’ programmes and they are widely used in body transformation courses. You can learn more about these approaches with our nutrition for body transformation article.

What is protein timing?

Protein timing is essential as it has a major impact on muscle protein synthesis (MPS), recovery, and overall exercise adaptations.  MPS is, to put it simply, the mechanism by which your body creates new muscle proteins. Your muscles sustain small amounts of damage during physical activity, and your body triggers MPS to help them recover and get stronger. Your muscles can heal and get stronger during this time since amino acids are used to generate new proteins. To optimise protein synthesis, research has shown that most people require a protein dosage of 20–30g at a meal. This amount includes about 3g of leucine, an essential amino acid that stimulates MPS.

In addition, spreading out this protein dose over three to four meals a day will help maximise MPS. Consuming protein during and after a training session is another protein timing tactic that helps restore muscle damage and improves adaptations related to hypertrophy and strength. It is widely acknowledged that to benefit from the well-known “anabolic window,” athletes should also consume protein before and/or after training. Although frequently cited at 30-60 minutes, the window is closer to 2-3 hours.

If using protein supplements, then other considerations may also need to be factored in. For more information, review our Optimal Protein Timing for Nutrition Supplements article.

High protein foods

Meat and Poultry lean, skinless poultry is a rich source of high-quality protein, and lean cuts of beef provide substantial amounts of protein along with essential vitamins and minerals.

Fish and Seafood The likes of salmon, tuna and cod are great sources of protein but fatty fish also contain omega-3 fatty acids which are beneficial for heart health. Prawns and shellfish are also low in fat and extremely high in protein.

Eggs eggs are a complete protein source, containing all essential amino acids, which can be a great addition to the diet.

Dairy Greek yoghurt is very high in protein, more so than natural yoghurt, and provides probiotics for gut health, while milk and cheese contain protein but also are a source of calcium.

Plant-based proteins tofu and tempeh are soy-based products that are popular among vegetarians and vegans for their high protein content. Beans and legumes such as lentils, chickpeas and pinto beans are rich in both protein and fibre.

Protein supplements – whey protein which is derived from milk is a fast-digesting protein that is often used by athletes for a convenient high-quality source of protein.

Including a variety of protein sources in your diet ensures you receive a diverse range of amino acids.  It is important to consider both animal and plant-based options to ensure a diverse range of nutrients.  It’s equally important to consume high-quality protein if following a vegan or vegetarian diet, as plant-based proteins often don’t contain all essential amino acids.

The bulk of it

In the realm of athletic performance, understanding the science behind protein is fundamental for athletes aiming to maximise their potential. Protein plays a multifaceted role in muscle synthesis, recovery and overall physiological function. Athletes should adjust their protein intake based on individual needs, training goals and the nature of their sports. Incorporating a variety of high-quality protein sources in the diet, timing protein intake strategically and utilising whey or casein supplements can collectively contribute to enhanced sports performance and optimal recovery for athletes pursuing their goals.



Jäger, R., Kerksick, C.M., Campbell, B.I., Cribb, P.J., Wells, S.D., Skwiat, T.M., Purpura, M., Ziegenfuss, T.N., Ferrando, A.A., Arent, S.M. and Smith-Ryan, A.E., 2017. International society of sports nutrition position stand: protein and exercise. Journal of the International Society of Sports Nutrition, 14(1), p.20.

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