Nutrition Essentials For Training: Macros & Calories

Nutrition essentials for training cover the core nutrients and energy intake that directly support physical performance, recovery, and long-term adaptation to exercise.

Macros: Protein, carbohydrates and fats, along with total calorie intake, each play specific roles in how the body supports activity, repairs tissue, and responds to training stress.

This article explains how these nutrients function in the context of training performance.

Let’s dig in!

Macronutrients and Calories (Overview)

Macronutrients (macros) are what all foods can be broken down into, and most foods are made up of a combination of the three: protein, carbohydrates, and fats.

These are the core nutrition variables that make up your total calorie intake, also known as the amount of energy in the food you eat.

The amount of each macronutrient required is often personalised and depends on the individual and training load.

Micronutrients such as vitamins and minerals are also essential for health, but they are outside the scope of this guide.

Before going deeper into each, here’s a summary of what we will cover, their functions and how they affect fitness outcomes:

Component	Primary Function	When Demand Typically Increases	Performance Impact If Too Low
Protein	Muscle protein synthesis, Tissue repair, Adaptation, Lean mass maintenance	Resistance training, endurance training, higher training volume, calorie deficits	Impaired recovery, reduced training adaptation, loss of lean mass
Carbohydrates	Glycogen storage,  Moderate-to-high intensity energy production, Work capacity, Recovery	Endurance training, interval training, long-duration sessions, multiple sessions per week	Reduced power output, earlier fatigue and lower training quality in subsequent sessions
Fats	Stored energy, Maintenance of physiological homeostasis, Hormone production	Prolonged training phases, high overall energy expenditure	Hormonal disruption, impaired recovery signalling, reduced ability to tolerate high training loads
Calories	Training volume and intensity tolerance Maintenance of lean mass and body composition Recovery between sessions	As overall training volume and intensity increase	Impaired adaptation, increased injury risk, reduced performance capacity

TIP:
As training volume and intensity increase, overall food intake needs to increase.

Protein: Repair and Adaptation

Protein’s primary role in fitness is structural, used for growth and repair.

Key points: 

• Muscle protein synthesis

• The rate and quality of tissue repair

• Adaptation to repeated training stress

• Long-term lean mass maintenance

Training creates mechanical stress and microscopic damage to muscle fibres and connective tissue. Protein provides the amino acids (the building blocks) required to repair this damage and support adaptation with rest and recovery. (1, 2) 

Protein goes beyond just muscle growth; it’s also for other structural repair. It’s essential for ‘repairing’ your joints and tendons, and for reinforcing connective tissue and bones.

Higher protein intakes are associated with improved training adaptations and better preservation of lean mass compared to lower intakes, particularly when training volume or intensity is high. (3)

Protein is primarily used for growth and repair, but can be broken down for energy when energy demands exceed available carbohydrate and fat stores. This process, known as protein catabolism, provides amino acids for fuel (gluconeogenesis), effectively making lean mass a backup energy reserve during sustained deficits. (4)

A full breakdown of protein, how much you need, timing considerations, and more, see our guide Protein Essentials: What, When, and How Much 

TIP: 

1.6 grams of protein per kilogram of body weight per day is a safe average to aim for.

Carbohydrates: Energy and Capacity

Carbohydrates’ primary role in fitness is to supply energy for moderate-to-high-intensity training.

Key points:

• Glycogen storage in muscles and the liver

• Moderate-to-high intensity energy production

• Repeated effort capacity

• Recovery between demanding sessions

Carbohydrates are primarily stored in the body as glycogen, which serves as the body’s preferred fuel source during moderate-to-high intensity exercise, endurance sessions above low intensity, and repeated hard efforts.

Eating carbohydrates before and after training supports glycogen resynthesis, the process by which the body replenishes depleted glycogen stores in the muscles and liver following exercise. (5)

When glycogen availability is sufficient, athletes can maintain power output, sustain pace, and tolerate higher total training volume. (6,7)

When carbohydrate intake does not meet training demands, particularly during long-duration sessions or frequent training weeks, reductions in power output, earlier fatigue, and lower-quality subsequent sessions are commonly observed. (8,9)

Carbohydrates do not directly drive adaptation like protein, but they enable the training intensity required for meaningful training stress and adaptation while providing energy for recovery. (10)

Timing is also important; consuming carbohydrates 1–3 hours before training and replenishing them within the first few hours after exercise helps restore glycogen and support subsequent sessions. (11)

For endurance events lasting longer than 150 min, the optimal range to aim for is 60-90 g of carbohydrates per hour, with lower intakes of 30-60 g per hour for sessions lasting 60-150 min. (11)

TIP:
The feeling of “Hitting the wall” is largely caused by depleted glycogen, reducing muscle output.

Fats: Necessary and Supportive

Fats are more than just a dense energy source. Their primary roles in the body and fitness are energy storage, physiological function, and hormonal regulation.

Key points:

• Stored energy

• Maintenance of physiological functions

• Hormone production (testosterone, estrogen, cortisol)

• Cell membrane structure and integrity

Fats are especially suited for energy storage, providing more than twice the energy per gram compared to carbohydrates or protein.

In the body, fats are primarily stored as triglycerides, which can be broken down into fatty acids and glycerol and released into the bloodstream to supply energy, particularly during lower-intensity and longer-duration activity. (12)

Both carbohydrates and fats are your body’s preferred energy source. The key difference is speed: carbohydrates supply energy quickly, while fats are metabolised more slowly, making them better suited for sustained energy demands rather than high-intensity efforts. (5)

Fat metabolism is part of a continuous biological cycle of storing, breaking down, and using fats for energy and cellular function. (13)

Fats also serve other essential structural roles in the body; they form cell membranes, support cellular communication, and participate in chemical signalling that regulates growth, immune function, reproduction, and metabolism. (13)

Fats are critical for hormone synthesis and physiological function. Inadequate fat intake can disrupt these systems and negatively affect muscle growth, bone health, and reproductive function. (14)

The four primary dietary fat types:

Monounsaturated fats – commonly found in olive oil, avocados, and nuts.
Polyunsaturated fats – including essential fatty acids such as omega-3 and omega-6.
Saturated fats – found in animal products, dairy, and some tropical oils.
Trans fats – mostly produced through industrial processing and generally recommended to be minimised.

More details on each type can be found here.

TIP:
Omega-3s and 6s are ‘essential’ because your body cannot produce them; they must come from your diet.

Calories: Energy Availability and Balance 

Calories represent the total potential energy contained in food. Calories, or energy availability, form the foundation for all macronutrient functions.

Without sufficient energy intake, even optimal protein, carbohydrate, and fat intake cannot fully support training adaptation, recovery, or performance.

Key points:

• Total energy contained in food

• Energy provided by macronutrients

• Energy balance and body weight regulation

• Individual energy needs based on body size, type and training demand

During digestion, this energy from food is released and either used immediately for bodily processes and physical activity or stored for later use, depending on the body’s needs. (15)

Each macronutrient contributes energy:

Protein provides 4 kcal per gram
Carbohydrates provide 4 kcal per gram
Fats provide 9 kcal per gram

Daily calorie needs vary widely depending on body size, muscle mass, sex, age, and especially training volume and intensity. (16)

Energy balance, often simplified as “calories in vs calories out”, determines whether body weight increases, decreases, or remains stable. However, biological factors such as digestion efficiency and hormonal responses can influence how the body processes and uses those calories. (17)

When calorie intake consistently exceeds the body’s needs, the surplus energy is largely stored as body fat. (18) 

On the other hand, a sustained calorie deficit will lead to weight loss, as stored energy is used up to meet demand. One caveat to this is that without adequate protein, lean muscle mass can degrade, too, as your body can break down your tissue for energy (as discussed earlier, gluconeogenesis). (19)

Tracking calorie intake alongside regular body weight weigh-ins can help individuals better understand their energy balance and make practical adjustments over time. 

Research has shown that frequent self-weighing is associated with improved weight management behaviours and greater weight loss outcomes. (20)

TIP:
You can find a simple total daily calorie calculator here. 

And can use options like these to track your calories. 

Is This For You?

Training creates the stimulus for adaptation and nutrition provides the resources that allow those adaptations to occur.

When calorie intake roughly matches training demands, the body has the energy required to train consistently, repair tissue, and adapt to stress.

Learning how much to eat without calorie tracking is a skill that develops over time. A simple place to start is focusing on protein, we’ve covered this and how to hit your daily targets in our article protein maths.

Once these foundations are in place, other recovery strategies such as sleep, hydration, and supplementation have a solid base to work from.

Have any questions or suggestions? Feel free to contact us here.

References:

1. Xu, F., Zeng, J., Liu, X., Lai, J. and Xu, J., 2022. Exercise-induced muscle damage and protein intake: a bibliometric and visual analysis. Nutrients, 14(20), p.4288. https://pmc.ncbi.nlm.nih.gov/articles/PMC9610071/
2. Stožer, A., Vodopivc, P. and Križančić Bombek, L., 2020. Pathophysiology of exercise-induced muscle damage and its structural, functional, metabolic, and clinical consequences. Physiological Research, 69(4), pp.565–598. https://pmc.ncbi.nlm.nih.gov/articles/PMC8549894/
3. Nunes, E.A., Colenso-Semple, L., McKellar, S.R. et al., 2022. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. Journal of Cachexia, Sarcopenia and Muscle, 13(2), pp.795–810. https://pmc.ncbi.nlm.nih.gov/articles/PMC8978023/
4. Sanvictores, T., Casale, J. and Huecker, M.R., 2023. Physiology, fasting. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK534877/
5. Naderi, A., Rothschild, J.A., Santos, H.O. et al., 2025. Nutritional strategies to improve post-exercise recovery and subsequent exercise performance: a narrative review. Sports Medicine, 55, pp.1559–1577. https://link.springer.com/article/10.1007/s40279-025-02213-6
6. Hargreaves, M. and Spriet, L.L., 2020. Skeletal muscle energy metabolism during exercise. Nature Metabolism, 2(9), pp.817–828. https://pubmed.ncbi.nlm.nih.gov/32747792/
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8. Gonzalez, J.T. and Wallis, G.A., 2021. Carb-conscious: the role of carbohydrate intake in recovery from exercise. Current Opinion in Clinical Nutrition and Metabolic Care, 24(4), pp.364–371. https://pubmed.ncbi.nlm.nih.gov/33973552/
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10. Jeukendrup, A., 2014. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(S1), pp.S25–S33. https://pmc.ncbi.nlm.nih.gov/articles/PMC4008807/
11. Cao, W., He, Y., Fu, R., Chen, Y., Yu, J. and He, Z., 2025. A review of carbohydrate supplementation approaches and strategies for optimizing performance in elite long-distance endurance. Nutrients, 17(5), p.918. https://pmc.ncbi.nlm.nih.gov/articles/PMC11901785/
12. Muscella, A., Stefàno, E., Lunetti, P., Capobianco, L. and Marsigliante, S., 2020. The regulation of fat metabolism during aerobic exercise. Biomolecules, 10(12), p.1699. https://pmc.ncbi.nlm.nih.gov/articles/PMC7767423/
13. Crowley, R., 2024. What do fats do in the body? National Institute of General Medical Sciences. https://nigms.nih.gov/biobeat/2024/01/what-do-fats-do-in-the-body
14. Lowery, L.M., 2004. Dietary fat and sports nutrition: a primer. Journal of Sports Science and Medicine, 3(3), pp.106–117. https://pmc.ncbi.nlm.nih.gov/articles/PMC3905293/
15. Osilla, E.V., Safadi, A.O. and Sharma, S., 2022. Calories. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK499909/
16. Falcone, P.H., Tai, C.Y., Carson, L.R. et al., 2015. Caloric expenditure of aerobic, resistance, or combined high-intensity interval training using a hydraulic resistance system in healthy men. Journal of Strength and Conditioning Research, 29(3), pp.779–785. https://pubmed.ncbi.nlm.nih.gov/25162652/
17. Jumpertz, R., Le, D.S., Turnbaugh, P.J., Trinidad, C., Bogardus, C., Gordon, J.I. and Krakoff, J., 2011. Energy-balance studies reveal associations between gut microbes, caloric load, and nutrient absorption in humans. The American Journal of Clinical Nutrition, 94(1), pp.58–65. https://www.sciencedirect.com/science/article/pii/S0002916523023134
18. Hall, K.D., Heymsfield, S.B., Kemnitz, J.W., Klein, S., Schoeller, D.A. and Speakman, J.R., 2012. Energy balance and its components: implications for body weight regulation. The American Journal of Clinical Nutrition, 95(4), pp.989–994. https://pmc.ncbi.nlm.nih.gov/articles/PMC3302369/
19. Longland, T.M., Oikawa, S.Y., Mitchell, C.J., Devries, M.C. and Phillips, S.M., 2016. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss. The American Journal of Clinical Nutrition, 103(3), pp.738–746. https://pubmed.ncbi.nlm.nih.gov/26817506/
20. Steinberg, D.M., Bennett, G.G., Askew, S. and Tate, D.F., 2015. Weighing every day matters: daily weighing improves weight loss and adoption of weight control behaviors. Journal of the Academy of Nutrition and Dietetics, 115(4), pp.511–518. https://pmc.ncbi.nlm.nih.gov/articles/PMC4380831/