~ Annie Bothma, Elite Athlete, IOPN Performance Sports Nutritionist (EQF Level 7. Masters), Running & Strength Coach
In the ever-evolving fitness landscape, nutrition trends like low-carb diets, intermittent fasting, and calorie-restricted plans have gained mainstream popularity and falsely promise quick fixes and results. However, their suitability for athletes is questionable.
As an elite athlete myself, currently pursuing an Advanced Master's degree in Performance Nutrition, my goal is to help other athletes cut through the noise and follow a nutritional strategy that is not only going to optimize their performance, but also not compromise their long-term health.
I recently had to do an assignment on a 2018 Science article, "Swifter, Higher, Stronger: What's on the Menu?", by Professors Louise M. Burke and John A. Hawley.
In their article, Burke and Hawley emphasize that there is no universal "athletic diet." They advocate for personalized nutritional strategies tailored to the specific metabolic demands of different sports and the periodization of training and competition goals. The authors also explore the practical implementation of these strategies and address controversies in sports nutrition.
In this blog, I delve into the importance of personalized nutrition for athletes and examine why following trendy diets can often be detrimental. By understanding and applying individualized dietary practices, athletes can optimize their performance and maintain overall health.
Why There’s No One-Size-Fits-All Diet for Athletes
Different Goals Mean Different Nutritional Needs
Athletes pursue a variety of goals—some are building strength, others are training for endurance, while some aim to reduce body fat or maintain overall health. Each of these goals demands a distinct nutrition strategy:
Strength and Muscle Building
Requires higher protein intake alongside sufficient carbohydrates for energy during intense resistance training to stimulate muscle protein synthesis and optimize muscular hypertrophy. Creatine has been proven to be a safe and effective supplement for those who seek to improve muscle strength and power.
Endurance Sports
For endurance athletes, the focus should be on maximizing glycogen stores with carbohydrate-rich meals to sustain long-duration efforts. During prolonged exercise, strategic fueling with carbohydrate-based products like gels or sports drinks is essential to maintain energy levels and delay fatigue. Electrolyte intake through fluids becomes increasingly important to replace sodium and potassium lost through sweat, preventing dehydration and cramping.
Additionally, caffeine can be a powerful performance enhancer when used strategically, as it reduces perceived exertion and can help reduce cognitive fatigue. Consuming caffeine 30–60 minutes before or during longer efforts can improve endurance, but individual tolerance should be considered to avoid side effects like jitters or GI discomfort. Aim for 3-6 mg of caffeine/kg of body weight to optimize performance.
Weight Loss or Body Composition Changes
While calorie deficits are necessary for fat loss, extreme restriction can impair recovery, performance, and long-term health. Instead, a modest calorie deficit combined with resistance training and an increased protein intake is a more sustainable approach. This strategy helps preserve lean body mass while promoting gradual fat loss, ensuring athletes maintain their strength and performance during the process.
For instance, a sprinter will have vastly different macronutrient needs compared to a marathon runner. A lack of personalization could lead to under-fueling or nutrient imbalances that sabotage both performance and recovery.
Training Loads Vary Greatly
An athlete training for a marathon, ultra, or other high-volume events requires a significantly higher energy intake than someone who only goes to the gym a few times a week or engages in low-impact activities like walking. Trying to maintain a calorie deficit during high training loads not only slows recovery but also increases the risk of:
Injuries: Inadequate calories and nutrients impair bone density, leading to stress fractures and overuse injuries.
Hormonal Disruptions: Chronic under-fueling can suppress essential hormones like estrogen and testosterone, negatively affecting bone health and muscle repair.
Immune Suppression: Insufficient energy availability can weaken the immune system, leaving athletes more prone to frequent illnesses and infections.
Mood Disturbances: Low energy intake can negatively impact mood, leading to increased irritability, anxiety, and even symptoms of depression, all of which can affect motivation and performance.
Athletes need to ensure their energy intake matches their training demands to protect their health, optimize recovery, and sustain long-term performance.
Genetics and Metabolism Play a Role
Each individual processes nutrients and responds to training differently due to their unique genetic makeup. Here are some key examples:
Iron Absorption: Some people naturally absorb iron poorly, leading to deficiencies despite an iron-rich diet. Low iron is also very common among athletes who follow vegetarian or vegan diets.
Vitamin D Deficiency: People with darker skin are more prone to vitamin D deficiency because melanin reduces the skin’s ability to produce vitamin D when exposed to sunlight.
Fat Metabolism: Genetic predispositions can influence fat metabolism, making some individuals better adapted to high-fat diets while others may struggle. Interestingly, some studies have suggested that women may be slightly higher absolute fat a oxidation rate than men at the same intensities.
Food Allergies or Intolerances: Conditions such as lactose intolerance or celiac disease—an autoimmune disorder that requires the complete exclusion of gluten from the diet—demand careful dietary adjustments to meet nutritional needs while avoiding triggers.
Body Composition: Body size, muscle mass, and even the ratio of fast-twitch to slow-twitch muscle fibers play a significant role in determining caloric and macronutrient requirements. For instance, individuals with more fast-twitch fibers may excel in power-based activities but may require higher protein intake to support recovery.
Muscle Growth Potential: Some individuals genetically build muscle more easily (often due to higher levels of anabolic hormones or muscle fiber distribution), while others need to work harder to achieve similar results, impacting their nutritional needs.
Nutrient Conversion Efficiency: Genetics can also affect how efficiently the body converts nutrients like omega-3s or folate into their active forms, making supplementation or fortified foods necessary for some people.
Understanding these genetic and metabolic differences underscores the need for individualized nutrition strategies. Get to know your body and take note of how you respond to certain dietary and training interventions can help you eat and exercise in a way that is best suited to your strengths.
Lifestyle and Preferences Matter
Athletes don’t live in a bubble—preferences, work schedules, and travel all impact how we eat. A vegan athlete, for example, will need to carefully plan their diet to meet protein and iron needs. Similarly, shift workers or frequent travelers need portable and convenient options that fit their routine. A diet plan that doesn’t align with your lifestyle is unsustainable.
The most effective diet is one that you can consistently stick to, enabling you to perform at your peak as an athlete while staying healthy and injury-free.
Why Popular Fad Diet Trends Don’t Work for Athletes
Low-Carb Diets
Low-carb diets may be effective for weight loss or managing specific health conditions, but they’re generally not ideal for athletes. Carbohydrates are the body’s primary fuel source, replenishing glycogen stores in muscles that are essential for endurance, high-intensity performance, and recovery. Without adequate carbs, athletes risk chronic fatigue, reduced training capacity, and slower recovery. For example, a marathon runner following a low-carb diet might suffer from low blood sugar and hit the wall mid-run due to depleted glycogen stores, significantly hindering their performance.
Intermittent Fasting (IF)
Intermittent fasting, while simple and popular for its potential weight management benefits, often conflicts with the energy demands of athletes. Frequent, balanced meals are essential for fueling intense training sessions and optimizing recovery. Prolonged fasting periods can lead to muscle breakdown, decreased performance, and impaired recovery. For instance, an athlete skipping breakfast as part of an intermittent fasting routine might struggle to perform in an afternoon workout due to insufficient glycogen stores, ultimately compromising both their training and long-term progress. If your goal is to optimize muscle growth and strength, intermittent fasting may negatively impact your ability to increase muscle strength and size.
Calorie Deficits During High-Volume Training
Training for a marathon, ultra, or any high-volume event while in a calorie deficit—or under-fueling your training—sets the stage for long-term health problems. While a calorie deficit might reduce weight in the short term, the trade-offs include increased injury risk (e.g., stress fractures and tendinitis), muscle loss and slower recovery, and impaired immune function, making athletes more prone to illnesses.
Sustained under-fueling or being in a chronic state of low energy availability (LEA) can push athletes into Relative Energy Deficiency in Sport (REDs), as described in the IOC’s 2023 position stand. LEA occurs when there isn’t enough energy available to support both training demands and basic physiological functions, leading to a cascade of negative effects. REDs encompasses a range of physiological and psychological consequences, including:
Hormonal Disruptions: Suppressed production of sex hormones (e.g., estrogen and testosterone) can impair reproductive health and muscle repair.
Bone Health Issues: Decreased bone density and increased risk of osteoporosis and stress fractures.
Chronic Fatigue: Persistent energy depletion leads to reduced training capacity and overall exhaustion.
Cardiovascular Effects: Reduced heart rate variability and compromised heart health due to energy deficits.
Digestive Problems: Slower gastric emptying and nutrient malabsorption, leading to bloating or gastrointestinal discomfort.
Mental Health Impacts: Increased risk of depression, anxiety, irritability, and impaired focus, which can affect both training and daily life.
Reduced Metabolic Rate: The body adapts to chronic calorie restriction by slowing metabolism, making it harder to lose weight or maintain energy balance.
Chronically under-fueling your training has consequences that go beyond poor performance—they compromise long-term health and well-being. Athletes must prioritize adequate energy availability through proper nutrition to prevent these harmful effects, ensuring both optimal performance and longevity in their sport.
The Pillars of Individualized Nutrition
Assess Your Needs
Start by identifying your training load, goals, and dietary preferences. Tools like food diaries or professional assessments can provide valuable insights into your current nutrition habits. For a more accurate understanding of your body composition, an InBody scan or similar technology offers a detailed breakdown of lean body mass (muscle, bone, water content) and body fat percentage—information a regular bathroom scale simply cannot provide!
Frequent weigh-ins, however, can be a slippery slope for some athletes. Obsessing over the number on the scale may lead to restrictive eating habits or disordered eating patterns. Many athletes fall into the trap of believing that “lighter always equals faster,” convincing themselves they must constantly chase a specific race weight or arbitrary number to feel adequate or successful. This mindset not only undermines mental health but also often results in under-fueling, low energy availability (LEA), and compromised performance.
Rather than focusing solely on the weight on the scale, consider the bigger picture: your energy levels, performance, strength gains, recovery, and overall health. That is what really matters!
Match Energy Intake to Training Volume
Your energy requirements will fluctuate based on the volume and intensity of your training. In periods of intense training, focus on consuming calorie-rich foods and a balanced mix of macronutrients—emphasizing carbohydrates to maintain performance, while also prioritizing protein for recovery and ensuring adequate fats for overall health. On the other hand, during lighter training phases or rest days, modifying portion sizes and adjusting your macronutrient balance can assist in weight management while still fulfilling your basic energy needs.
Working with a sports nutritionist can help you determine how much carbohydrate you need to fuel your peak training blocks effectively. Scaling your plate to match your upcoming training sessions—adding more carbs for high-intensity days and reducing them for lower-intensity sessions—ensures you’re adequately fueled without overeating. This tailored approach helps optimize both training outcomes and overall energy balance.
Embrace a Food-First Approach, But Not a Food-Only Approach
While whole foods should always be your foundation, they are not the only tool in your nutrition toolbox. Prioritize whole foods for their nutrient density, bioavailability, and overall health benefits. A variety of fruits, vegetables, whole grains, lean proteins, and healthy fats should form the basis of your diet, ensuring you meet most of your nutritional needs naturally.
However, when deficiencies are identified through blood tests—such as low iron, vitamin D, or B12—a targeted supplement can be an effective way to restore levels to an optimal range. Supplements are particularly valuable when addressing deficiencies that are challenging to resolve through diet alone, supporting both athletic performance and long-term health.
For busy athletes who struggle to meet their protein targets, a protein shake can be a convenient and effective way to ensure adequate intake. This is especially true for vegans and vegetarians, who may find it difficult to achieve the recommended daily protein intake for athletes solely through plant-based foods. Protein shakes can play a crucial role in supporting muscle repair and recovery after training sessions.
Similarly, carbohydrate-based sports products like gels, chews, and drinks are specifically designed to fuel sustained performance during high-intensity or long-duration activities. These products provide quickly digestible energy, allowing athletes to maintain higher intensities for longer periods—a vital component for endurance sports.
While the focus should always be on a balanced, whole-food diet, supplements and performance products can be valuable tools to fill gaps, meet specific nutritional demands, and enhance your performance when used strategically. This balanced approach allows you to address your unique needs while keeping your health and performance at the forefront.
Be Strategic with Timing
When it comes to nutrition, timing matters just as much as what you eat. Strategic nutrient timing can optimize performance, recovery, and overall energy levels. Here are some key strategies to help you fuel effectively:
Fueling for Training
Pre-Training
Consuming a carbohydrate-rich meal or snack containing of 1-4g of carbohydrates per kg of body weight in the 1-4 hours before training sessions provides the glycogen stores your muscles need for sustained energy. For shorter timeframes, a smaller, easily digestible snack (like a banana, some dates or energy gel) 30-60 minutes before exercise can be effective.
During Training
For sessions lasting over 60-70 minutes or involving high-intensity efforts, use carbohydrate-based products like gels, chews, or sports drinks to maintain energy levels and delay fatigue. Aim for 60-90 g of carbs/hour during your training sessions.
Post-Training Recovery
Timing
Eating within 30-60 minutes after training can accelerate recovery. During this time, your muscles are most receptive to replenishing glycogen and synthesizing protein. Although the anabolic window might be larger than we initially believed, in my personal experience, the sooner athletes begin the recovery process, the better!
Carbohydrates and Protein
An ideal combination includes carbohydrates and protein—carbs restore glycogen levels, and protein aids in muscle repair. For instance, a smoothie made with fresh or frozen fruit, protein powder, and some milk or yogurt can be effective way to get in the nutrients you need to recover optimally after a training session.
Hydration and Electrolytes
Don’t forget to rehydrate and replace lost electrolytes, especially after long or sweaty sessions during summer time. Performing a sweat test where you measure the amount of fluid lost during training can help you determine your own individual fluid needs and better adjust your hydration strategy. This is an cheap and effective method that can be done at home.
Learn more: How to Do A Sweat Test
Conclusion: Cookie clutter plans or diets don’t work
Athletes are not machines, and there’s no “one-size-fits-all” solution for optimal performance and health. By ditching cookie-cutter diets and embracing personalized nutrition, you can fuel your body in a way that aligns with your unique goals, training, and lifestyle.
Remember, the right nutrition strategy isn’t just about performing well now—it’s about building a foundation for long-term health and athletic success.
If you need help finding the right nutritional strategy for you contact me at anniesathletes@gmail.com to get the support you need to optimize your health and performance.
References
Burke, L. M., & Hawley, J. A. (2018). Swifter, higher, stronger: What's on the menu? Science, 362(6416), 781–787. https://doi.org/10.1126/science.aau2093
Mountjoy M, Ackerman KE, Bailey DM, et al. (2023). International Olympic Committee Consensus Statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 57, 1073–1097. doi:10.1136/bjsports-2023-107397.
Jeukendrup, A., & Gleeson, M. (2024). Sport nutrition (4th ed.). Human Kinetics.
Jeukendrup, A. E., & Wallis, G. A. (2005). Measurements of substrate oxidation during exercise by means of gas exchange measurements. International Journal of Sports Medicine, 26(Suppl 1), S28–S37. https://doi.org/10.1055/s-2004-830512
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