Strength By Fitness

High-protein & Endurance training: Is that like cats & dogs, or the perfect symbiosis?

Welcome to another fact-based coaching article from Strength by Fitness.

Hägele, F.A., Herpich, C., Koop, J. et al. Short-term effects of high-protein, lower-carbohydrate ultra-processed foods on human energy balance. Nat Metab (2025). https://doi.org/10.1038/s42255-025-01247-4

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The Study.
A Metabolic Focus on Promoting Recovery and Training Adaptation

The role of dietary protein in athletic performance is well-established, particularly concerning its contribution to muscle hypertrophy. However, for endurance athletes, whose primary focus lies in cardiovascular fitness and sustained performance, protein nutrition is an equally critical component for the best possible recovery, training adaptations, maintained health, and ultimately enhanced, and injury free, endurance performance.

It is a fundamental principle in sports nutrition that individuals who engage in regular exercise training necessitate a higher intake of dietary protein compared to their sedentary fellow humans. A basic fact that does not change that every single obese, and overweight person on the planet would have a much easier time eating in a healthy, fat loss promoting way if they adopted a nutritionally rich, high-protein, higher-SPC food approach.

This increased protein & nutritional demand in general due to regular exercise arises from the physiological stresses imposed on the body during regular exercise activity. Duration, effort, and volume will also affect this increased need.

Necessitating adequate protein for muscle repair and remodeling processes in order to not just maintain, and improve performance, but to remain injury free, and healthy too.

Scientific investigations like this endurance, protein focused study into the specific protein needs of endurance athletes aim to provide evidence-based guidelines that address the total daily protein requirement to support endurance athletes’ metabolic demands.

Many endurance athletes typically consume a daily protein intake of around 1.5 grams per kilogram of body mass. While this is already really good, we can still do better.

Contemporary studies have since long established that protein requirements suggest that a daily intake of approximately 1.6 to 1.8 grams per kilogram of body mass should be advocated for the active fitness population during standard training. In part based on the simple fact that protein related outcomes, and protein synthesis itself seems to almost universally be maxed out around 1.6g per kg and day, all while older people, and plant-based people need slightly more protein to reach full amino acid levels, and equal outcomes due to differences in bioavailability, and absorption.

The general protein recommendation represents a significant increase compared to the 0.8 grams per kilogram of body mass per day that´s long been recommended for sedentary adults that wish to maintain basic functions, and health.

This new endurance athletes and protein intake study highlight the elevated protein needs associated with endurance training.

It is important to note that this requirement is not static and can be further elevated under specific conditions, as I have already mentioned in this article.

For instance, during periods of carbohydrate-restricted training, when the body might rely more on protein for energy, the daily protein requirement may exceed 2.0 grams per kilogram of body mass.

The Luteal Phase and Female Athletes.

Similarly, on rest days, protein remains crucial for muscle repair and recovery from previous training bouts, also necessitating a higher protein, higher-SPC intake. Some minor evidence suggests that female endurance athletes may experience a minutely increased protein need, particularly during the luteal phase of their menstrual cycle, where intakes up to 1.9 grams per kilogram of body mass per day might provide to be beneficial. Although, I would like to point out that this conclusion of this study is kind of highlighting something very trivial when they lift out the luteal phase for women.

After all, all female athletes should be on a 1.8+ high-protein intake every day of life already, just like male athletes.

The slight variability in these recommendations in this study underscores the multifaceted interplay of training intensity, dietary strategies, satiety, and individual physiological factors in determining optimal protein intake.

However, let this big pillar coach save you countless of time, and focus.

The real life differences between a 1.8, 1,9, or 2.0 gram of protein per kg of bodyweight and day are miniscule. So why would you worry about having it perfectly dialed in? In fact, the hypertrophic difference between 1.6 and 2.0 is already very small.

 In other words, since protein also favor vastly better nutrients per unit of energy food habits, just make it a habit of consuming around 2.0 grams of protein/kg/day together with making every meal a higher-SPC meal.

No matter how fit you are, or overweight with excess body fat to lose.

Instead of worrying about the exact intake thats optimal do this.

If you have excess body fat to lose, dial your protein intake up even more, beyond 2.0.
If, on the other hand, you are losing too much body fat, and feel that exercise performance, recovery and progression is suffering, dial down the SPC factor jut a little bit, by primarily adding more plant-based whole carbs from fruit, and berries, this is easy, high quality energy loaded with micronutrients, unless you can make room for one more meal per day.

Becoming to lean is also detrimental.

Excess body fat has no health benefits, and neither does it help any athletes outside of maybe heavy weight powerlifters. But, having too little body fat actively harms fitness performance, and health, so if you are becoming too lean, add one meal, and or lower the SPC by consuming more easy energy foods loaded with health promoting micronutrients, such as fruit, and berries. Heck in this situation, even low SPC foods such as dried dates can be a great choice.

Beyond the total daily intake, the timing and distribution of protein consumption throughout the day have been a topic of discussion. While earlier research suggested aiming for a per-meal protein intake of approximately 0.5 grams per kilogram of body mass to maximally stimulate the synthesis of contractile muscle proteins, recent evidence indicates that the human body can absorb and utilize a larger amount of protein per meal.

Studies suggest that muscle protein synthesis (MPS) can be maximized with intakes ranging from 40+ grams of high-quality protein per meal, depending on factors like body size and activity level.

Current research even highlight that the anabolic responses related to protein might continue to increase with protein ingestion close to 100 grams of protein per meal.

While spreading protein intake evenly throughout the day to maintain a consistent stimulus for MPS remains a valid approach, it is the total daily protein intake that is the primary driver of muscle adaptation, health outcomes, fat loss, and total food consumption.

 Athletes can effectively meet their protein needs by distributing their intake across 3-4 meals, or even potentially fewer larger meals, particularly when a significant portion of the daily protein is consumed around workout sessions.

Consuming protein before, during, and within three hours after your exercise session within a is highly beneficial for recovery and muscle protein synthesis. No, you do not have to do all three.

I prefer eating a high-protein meal 2 hours before my workouts, and another high-protein meal within 3 hours of my workout, in both cases, both meals are also rich in whole plant-based carbs, and micronutrients.

Protein Type, and quality, all proteins are not the same, but you can also just eat much more of the lower quality proteins.

The type of protein consumed can also influence recovery and training adaptation. Especially so for people on a lower protein intake.

Plenty of studies have highlighted the benefits of ingesting high-quality proteins, such as whey, soy, pea isolate, and Quorn within 3 hours after exercise, and or 2 hours prior to exercise.

As these higher protein sources can significantly improve muscle recovery and promote hypertrophy. 

Protein quality is determined by its ability to provide adequate quantities of the essential amino acids that´s required for protein synthesis, maintained, and improved health and fitness performance.

Leucine, a branched-chain amino acid, has been identified as a key stimulator of skeletal muscle protein synthesis, making protein sources rich in leucine particularly valuable for endurance athletes.

Multiple daily whole high-quality protein sources should be the primary focus, but protein supplements can offer additional convenience and benefits for exercise performance, fat loss, health, satiety and recovery.

At Strength By Fitness it is our longstanding recommendation to maintain a food plan that makes of 3 to 4 main protein sources per day. This ensures a wider micronutrient intake, and better amino acid levels. Especially important for the elderly, and the plant-based, but also beneficial for most omnivores, since billions of omnivores are nutritionally deficient.

The benefits of adequate protein intake for people in general, and endurance athletes extend beyond just muscle protein synthesis.

Research suggests that protein play a supportive role in muscle glycogen resynthesis, particularly when carbohydrate intake is suboptimal.

While carbohydrates remain the primary fuel source for glycogen replenishment, the addition of protein will aid in this process when sufficient carbohydrate intake (1.2 g/kg BM/hour for competitive endurance athletes ) is challenging to achieve during the race, as well as post workout/race.

However, when carbohydrate recommendations are met, adding protein does not appear to provide additional benefits for glycogen restoration. Because you are already consuming enough carbs to saturate your glycogen stores.

Adequate protein intake is crucial for attenuating post-exercise muscle protein breakdown, especially in catabolic states such as an energy deficit.

This is particularly important for endurance and strength training athletes who often engage in prolonged and intense training sessions that leads to muscle damage, and physical exhaustion.

Protein also plays a role in optimizing the metabolic response, and health, relative to not just endurance training, but all forms of exercise especially under conditions of low carbohydrate and/or energy availability.

The current body of research strongly supports the notion that endurance athletes require a higher daily protein intake than sedentary individuals, with a recommendation of approximately 1.8 grams per kilogram of body mass on standard training days, as your minimum high-protein intake.  

Per meal intake, again.

While earlier recommendations emphasized distributing protein intake evenly throughout the day with a per-meal target of around 0.5 grams per kilogram of body mass, current understanding suggests that total daily intake is more critical, and athletes can effectively meet their needs with varied meal frequencies and potentially larger protein doses per meal, particularly around workout times. Prioritizing high-quality protein sources rich in essential amino acids remains crucial for maximizing muscle protein synthesis, recovery, and training adaptation. While protein can assist in glycogen resynthesis under specific conditions, it is not a substitute for adequate carbohydrate intake when the primary goal is glycogen restoration. For endurance athletes aiming to maintain a healthier and fitter lifestyle through exercise and good food habits, prioritizing a big enough protein intake is a cornerstone of optimal nutritional support for their training, longterm health, and recovery needs.

About the image.

The role of protein nutrition for optimizing endurance performance is no different than what happens when we lift weights. It promotes better exercise related adaptations and enhance post-exercise recovery.

Dietary protein intake is an important factor in facilitating muscle glycogen resynthesis under conditions of suboptimal carbohydrate (CHO) intake, and stimulating better muscle protein synthesis rates during recovery. It attenuates post-exercise protein breakdown in catabolic states such as energy restriction and replenish oxidative amino acid losses during exercise.

A higher protein intake provides more of the needed amino acids that are responsible for the repair and adaptation of skeletal muscle proteins, connective tissue, and even our organs.

Muscle protein synthesis and muscle protein breakdown are both stimulated during and after both endurance and resistance training. This process powers the resulting outcome of skeletal muscle adaptation to all fitness modalities which you do on a regular basis, even more so when you provide sufficient stimulus, nutrition ( getting enough protein & energy are major food pillars ), and recovery over time.

In addition to the multi-faceted progression of type 1, and 2 muscle fibers, new mitochondrial proteins that power energetics also adapt, and progress in response to the same physical activity, and exercise, with a clear impact for both strength & endurance performance.

Everything that needed to be said has already been covered. So lets wrap this up with our Strength By Fitness higher-SPC, high-protein big pillar approach.

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