When working with clients who are trying to lose fat while maintaining or even improving performance in the gym, a common issue I encounter is they are eating insufficient carbohydrate intake for performance. Many people, influenced by diet trends and misinformation, believe that cutting carbs is the most effective way to shed body fat. While reducing carbs can have its place in certain contexts, it often leads to significant drops in energy, poor workout performance, and even stalled progress if not approached correctly.
Insufficient Carb Intake for Performance: The Low-Carb, Low-Energy Dilemma
Let’s consider a typical client scenario. A highly motivated individual comes to me, eager to achieve fat loss while maintaining a rigorous training schedule. However, despite their dedication, they struggle with persistent fatigue, sluggish workouts, and an overall lack of progress. They have meticulously reduced their carbohydrate intake, believing that fewer carbs will fast-track their fat loss journey.
Initially, they maintain their protein intake and incorporate healthy fats, assuming this balance will provide sufficient energy. However, they soon begin experiencing extreme exhaustion, brain fog, and noticeable reductions in both strength and endurance. Their once-productive workouts feel laboured and ineffective, and they find it increasingly difficult to push through their training sessions. Recovery periods become extended, leading to prolonged muscle soreness and decreased motivation. Additionally, they notice mood swings, irritability, and an overall sense of depletion, all of which are symptoms commonly associated with inadequate glycogen replenishment.
As we assess their dietary approach, it becomes evident that the drastic carbohydrate restriction has led to an energy deficit that is negatively impacting not just their workouts, but their daily life as well. Without sufficient glycogen stores, their body struggles to sustain the high-intensity efforts required for effective training. Their metabolism also begins to adapt to this under-fueled state, making fat loss more difficult over time. They are left in a cycle of underperformance, frustration, and stalled progress, highlighting the importance of a well-balanced approach to nutrition that includes strategic carbohydrate intake.
Understanding the Role of Carbs in Performance
Carbohydrates are the body’s preferred fuel source for exercise, particularly for strength training, high-intensity interval training (HIIT), and endurance spCarbohydrates are the body’s primary and most efficient energy source, playing a crucial role in fueling all types of physical activity, particularly strength training, high-intensity interval training (HIIT), and endurance-based exercises. When an individual engages in demanding workouts, their body relies on glycogen, a stored form of carbohydrates in the muscles and liver, to provide the necessary energy. Without an adequate carbohydrate intake, these glycogen stores become rapidly depleted, leading to a noticeable decline in performance.
Clients who do not consume enough carbohydrates often experience a range of negative symptoms, including:
- A significant drop in strength and power output during workouts
- Poor endurance and an inability to sustain prolonged physical exertion
- Increased muscle soreness and delayed recovery times, making it harder to train consistently
- A decrease in motivation and mental clarity, making workouts feel exhausting and ineffective
Moreover, chronic carbohydrate restriction forces the body to rely on alternative energy sources, such as protein and fat. While fat oxidation can support lower-intensity exercise, it is not an optimal fuel for high-intensity training. The body may even begin breaking down muscle tissue to produce glucose, which can lead to muscle loss over time.
Additionally, a prolonged low-carb intake can lead to heightened cortisol levels, the stress hormone that, when elevated for extended periods, can contribute to fat retention, increased cravings, sleep disturbances, and overall metabolic inefficiencies. In extreme cases, individuals may experience symptoms such as dizziness, brain fog, and even hormonal imbalances, all of which can severely impact athletic performance and daily functioning.
In short, overly restricting carbohydrates can be counterproductive, slowing progress rather than accelerating it. Rather than eliminating carbs entirely, the key is to find a balanced intake that supports energy levels, enhances training intensity, and promotes sustainable fat loss while maintaining overall well-being.
So, what do we do when we suspect a client is eating an insufficient carb intake for performance?
Assessing Calorie And Macronutrient Needs
When you suspect a client is eating an insufficient carb intake for performance, the first step in tackling it is assessing the situation more thoroughly. Assessing calorie intake is the cornerstone of any effective nutrition plan, especially when trying to balance fat loss with optimal performance.
Many individuals unknowingly consume too few calories in an effort to shed fat, leading to diminished energy levels, impaired recovery, and overall lethargy. When I work with clients, I first evaluate their total daily energy expenditure (TDEE) and compare it to their actual caloric intake to determine whether they are in an appropriate deficit.
We have a variety of calculators on site that will help you with this assessment:
Beyond calorie intake, macronutrient distribution plays a critical role in performance. While some individuals hyper-focus on cutting carbohydrates, they often neglect the importance of protein and fat balance. Protein intake should be sufficient to preserve lean muscle mass, particularly in a caloric deficit, and fat should be adequately included to support hormonal health and stabilise hunger. Without a proper balance of these macronutrients, performance in the gym and overall well-being can suffer.
I also take into account the client’s activity level, training intensity, and personal goals. An endurance athlete, for example, will have different carbohydrate and protein needs compared to someone focused on resistance training or general fat loss.
There are two primary scenarios that this initial assessment turns up:
- Excessively Low-Calorie Intake: If a person’s overall caloric deficit is too aggressive, their body lacks sufficient energy to sustain workouts, recover effectively, and maintain muscle mass. When calories are too low, metabolic adaptations occur, often leading to fatigue, hormonal imbalances, and even plateaus in fat loss. The first priority in this case is gradually increasing caloric intake to a more sustainable level while maintaining a moderate deficit that allows for fat loss without compromising performance.
- Inadequate Carbohydrate Intake But An Appropriate Calorie Deficit: Some individuals may be in an appropriate overall calorie deficit but have a disproportionate macronutrient split, specifically too few carbohydrates. Since carbs are the body’s preferred fuel for high-intensity exercise, insufficient intake can cause sluggish workouts, prolonged recovery times, and an overall decline in physical output. The key in this case is simply a more appropriate macronutrient distribution, and effectively, adding more carbs in while maintaining the overall calorie balance.
In both scenarios, fine-tuning intake is crucial. Whether it’s increasing overall calories to prevent excessive stress on the body or reallocating macronutrients to improve workout performance, the goal is to fuel the body efficiently while still progressing toward fat loss objectives.
Further Assessment: Calorie And Carbohydrate Distribution
Another crucial factor in assessing caloric and macronutrient needs is meal timing. Many clients who experience poor performance are not only under-eating but also spacing their meals too far apart or failing to consume pre- and post-workout nutrition appropriately.
When meals are too spread out or poorly balanced, the body struggles to maintain stable blood sugar levels, leading to fatigue, mood swings, and suboptimal training performance. Proper meal timing ensures a steady flow of nutrients, providing the necessary energy to fuel workouts and enhance recovery.
Pre- and post-workout nutrition plays a pivotal role in optimising performance. A well-balanced pre-workout meal consisting of complex carbohydrates and lean protein ensures glycogen stores are topped up, allowing for better endurance and power output. Post-workout, rapid glycogen replenishment through nutrient-dense carbohydrates combined with high-quality protein aids in muscle repair, reduces soreness, and prepares the body for subsequent training sessions.
Adjusting meal composition and timing to align with training demands can significantly enhance both energy levels and overall progress. Even when someone has an insufficient carb intake for performance, correctly timing the carbs that they do eat, can lead to better performance.
Many clients who try to eat too few carbs also fall victim to the worst-case scenario, where they experience all the downsides of dieting but see none of the results. This often occurs due to excessive restriction, which leads to uncontrollable hunger and binge eating, particularly on weekends. When a client severely restricts carbs throughout the week, they create a cycle of depletion and overcompensation. By Friday or Saturday, cravings intensify, leading to overindulgence in high-calorie, processed foods, effectively negating their weekly deficit.
To break this cycle, I assess a client’s dietary habits, hunger signals, and emotional relationship with food. Implementing structured carb intake throughout the week, particularly around workouts, helps regulate appetite, reduce cravings, and promote sustainable fat loss.
Rather than an all-or-nothing approach, I encourage clients to adopt a balanced, consistent nutritional strategy that allows for flexibility while preventing extreme fluctuations in energy and dietary adherence. Over time, this method leads to better satiety, improved performance, and a more positive experience with dieting.
My Coaching Approach: Strategic Carb Integration
To help clients regain energy and performance while still aligning with their fat loss goals, I take a strategic approach to carbohydrate intake:
- Gradual Reintroduction of Carbs: Rather than an abrupt increase, I slowly add carbs back into their diet, often starting with pre- and post-workout meals. This generally allows for the carbs they do eat to directly contribute to their training performance and recovery. If they have been eating too few calories, we add calories back as carbs, aiming to restore calories back to an appropriate level. If their caloric intake is already appropriate, we redistribute calories by reducing fats and increasing carbs (while ensuring fats do not drop below ~0.5g/kg of body weight).
- Prioritising Quality Carbohydrates: I emphasise whole, nutrient-dense carbohydrate sources such as potatoes, brown rice, quinoa, oats, and fruits. These complex carbs provide a steady energy release, essential micronutrients, and fibre for improved digestion. Avoiding processed and refined carbs ensures that clients get maximum nutritional benefits while preventing blood sugar spikes and crashes.
- Strategic Carb Timing for Optimal Performance: Timing carbohydrate intake around workouts enhances training efficiency. Pre-workout carbs provide immediate energy for strength and endurance, reducing muscle fatigue, while post-workout carbs replenish glycogen stores and accelerate recovery.
- Monitoring Performance Metrics and Adjusting Accordingly: I track key performance indicators such as strength levels, stamina, mental focus, and recovery time. Regular assessments allow us to fine-tune carb intake based on individual responses. Clients typically experience notable improvements in their ability to push harder during workouts within one to two weeks of reintroducing carbs.
- Tailoring Carb Intake to Individual Needs: Every client has unique metabolic demands, body types, and training styles. Some individuals may still require a relatively lower-carb (and lower calorie) approach, but that generally doesn’t mean eliminating them entirely. But we should be able to find a level of intake that ensures that they achieve both fat loss and have good performance.
Ultimately, achieving the right balance between caloric intake and macronutrient distribution requires a strategic and individualised approach. Rather than focusing on cutting carbs indiscriminately, I try to guide clients toward a well-structured, evidence-based nutritional strategy that fuels their performance while still allowing for effective fat loss.
The Results: More Energy, Better Workouts, and Sustainable Fat Loss
Once clients start fueling their bodies properly, they generally experience a drastic turnaround. Energy levels surge, workouts become more effective (and fun), and fat loss feels a lot more effortless, rather than a constant struggle against fatigue. Clients also tend to develop a healthier relationship with food, understanding that carbohydrates are not the enemy but a key component of optimal performance and well-being.
If you’ve been avoiding carbs in the hope of accelerating fat loss but find yourself drained and unmotivated, it might be time to reassess. Fat loss and performance can co-exist, but for most individuals, that means keeping carbs in the game.
Client case studies, such as this case study on helping a client deal with insufficient carb intake for performance, are a phenomenal way to learn how to coach someone. While we teach people how to coach exercise, there is just so much to learn and you often need examples to illustrate the concepts.
Unfortunately, you can’t really find these online, and it leads coaches to make the same mistakes over and over, and it makes it difficult for coaches to know what to do. They end up feeling lost and unsure.
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Paddy Farrell
Hey, I'm Paddy!
I am a coach who loves to help people master their health and fitness. I am a personal trainer, strength and conditioning coach, and I have a degree in Biochemistry and Biomolecular Science. I have been coaching people for over 10 years now.
When I grew up, you couldn't find great health and fitness information, and you still can't really. So my content aims to solve that!
I enjoy training in the gym, doing martial arts and hiking in the mountains (around Europe, mainly). I am also an avid reader of history, politics and science. When I am not in the mountains, exercising or reading, you will likely find me in a museum.