Do You Really Need To Have Sugar For Your Workouts?

You’re midway through an intense workout, sweat dripping, muscles burning, and suddenly—you feel exhausted. Your energy plummets, your movements slow, and every rep feels ten times heavier. Was it because you skipped the pre-workout snack? Did you not fuel properly? Or, more specifically, do you actually need sugar to power through your workout?

The debate over sugar in exercise is heated. Some athletes swear by intra-workout carbs to keep their energy levels steady, while keto advocates argue that sugar is unnecessary and that the body can adapt to burning fat instead. So, who’s right?

In this article, we’ll break down the role of sugar in training, when it’s essential, when it’s overrated, and what alternatives exist for those who prefer to keep their workouts low-carb or fasted.

Is sugar a must for every workout? The short answer is not necessarily.

The body has different energy systems that fuel our movements and allow us to function effectively. The primary energy systems at play during exercise are:

1. Phosphagen System (ATP-PCr) – This system provides immediate energy for short bursts of high-intensity efforts lasting for 10 seconds. It doesn’t rely on sugar but instead uses stored ATP and creatine phosphate. Example of activities:

• 1-rep max deadlift or squat
• 10-second all-out sprint
• Olympic weightlifting
• Jumping or plyometric drills
• Max-effort throws (Javelin or shot put)

2. Glycolytic System (Anaerobic Glycolysis) – This system kicks in for moderate to high-intensity efforts lasting 30 seconds to 2 minutes. It breaks down glucose (from stored glycogen or circulating blood sugar) into ATP, making sugar the dominant fuel source. Example of activities:

• High-intensity interval training (HIIT)
• 400m sprint
• Circuit training
• CrossFit-style workouts
• Repeated sets of heavy lifting (8-12 reps)

3. Oxidative System (Aerobic Metabolism) – For lower-intensity, sustained efforts like endurance training and jogging, the body shifts to burning both carbohydrates (glucose/glycogen) and fat for energy. Examples of activities:

• Long-distance running (5K, 10K, marathons)
• Cycling
• Rowing
• Swimming long distances
• Hiking
• Brisk walking

Pre-workout carbs

In essence, the body needs to use carbohydrates (sugar) as an energy source. But sugar is not the only source of energy that our body can use. Sometimes, your sugar stores are already enough for your workout session, and supplementing with more sugar can derail you from achieving your fitness goals.

Supplementing your body with slow-digesting carbs is recommended to keep you energized throughout your workout. This is ideally done as your pre-workout meal or snack. Here are some examples of pre-workout carbs:

• Oats
• Whole wheat toast with honey
• Sweet potatoes
• Fruit smoothies
• Whey protein shake
• Greek yogurt
• Mass gainer shakes
• White rice

Here’s a plan for women that will help you get strong and lean:

Same for men:

During explosive, high-intensity efforts, muscles rely primarily on glycogen stores. If glycogen is depleted, performance can suffer, leading to early fatigue, reduced power output, and difficulty completing reps.

Glycogen depletion becomes a real issue if you train for more than 60-90 minutes. Endurance athletes often take in sugars mid-session to prevent “bonking” or hitting a performance wall.

In these cases, intra-workout sugar can help sustain energy and maximize performance. Here are some examples of quick-digesting sugars that can give you quick energy:

• Sports drinks
• Energy gels
• Dates
• Bananas
• Honey
• Rice cakes
• Coconut water

1. Fasted training

Some people train in a fasted state to improve fat oxidation and metabolic flexibility. Low-intensity, steady-state cardio can be done effectively without sugar since fat can be a primary energy source. Those following a ketogenic diet adapt to using fat and ketones instead of glucose, making sugar intake unnecessary for their performance.

If your workout is brief and moderate in intensity, your stored glycogen is likely sufficient, and consuming sugar won’t provide a noticeable benefit. In fact, spiking insulin when it’s not needed can blunt fat burning and cause unnecessary energy crashes.

Not all sugars are created equal, and choosing the right type can make a big difference in your performance and recovery. Here’s a breakdown of the most common types of sugars used in training and when they are most effective:

Best for: HIIT workouts, weightlifting, sprinting, long-distance running, cycling, or any session lasting over 60 minutes.

These sugars are quickly absorbed into the bloodstream, providing an instant boost in blood glucose. It is ideal for high-intensity and endurance workouts that require rapid energy replenishment.

• Glucose (Dextrose): The simplest and fastest-absorbing carbohydrate, often found in sports drinks and energy gels. It’s an excellent choice for immediate fuel during prolonged or intense training.
• Maltodextrin: A processed carbohydrate that breaks down quickly, making it useful for intra-workout fueling without causing stomach distress.
• Sucrose (Table Sugar): A combination of glucose and fructose, it provides a quick energy source but isn’t as efficient as pure glucose for fast absorption.

Best for: Pre-workout meals (30-90 minutes before training) for sustained energy without blood sugar fluctuations.

Some forms of carbohydrates digest more slowly, providing steady energy rather than a sudden spike. These are useful for pre-workout meals to avoid energy crashes.

• Fructose (Fruit Sugar): Found in fruits and honey, fructose digests slower than glucose and must be processed by the liver. While it can provide a steady release of energy, too much can lead to digestive discomfort.
• Complex Carbohydrates (Oats, Sweet Potatoes, Whole Grains): These break down more gradually, ensuring a prolonged energy supply without rapid spikes or crashes.

If you’re following a ketogenic diet or prefer fasted workouts, your body primarily relies on fat and ketones for energy instead of glucose. Keto-adapted athletes can perform well without sugar, especially in lower-intensity activities like walking, steady-state cardio, or even moderate resistance training.

However, high-intensity efforts still require some level of glycogen. If you’re keto but engaging in demanding workouts (like CrossFit, sprinting, or powerlifting), targeted carbohydrate intake (e.g., small amounts of glucose pre- or intra-workout) can enhance performance without kicking you out of ketosis.

For fasted training, the benefits lie in increasing fat oxidation and metabolic flexibility. But for strength training or intense exercise, prolonged fasting may lead to performance declines due to depleted glycogen levels. A good compromise is consuming essential amino acids (EAAs) or small amounts of slow-digesting carbs to prevent muscle breakdown while keeping insulin levels low.

So, do you really need sugar?

The answer depends on your training style, workout duration, and dietary approach. Yes, you need sugar if you’re doing high-intensity workouts, long-duration endurance training, or need rapid energy replenishment.

If you’re doing low-intensity workouts, training in a fasted state, or following a keto diet, you can skip the sugar.

Ultimately, sugar is a tool—one that can enhance or hinder your performance depending on how and when you use it. Knowing when to fuel with sugar and when to rely on fat-burning mechanisms will help you optimize both your workouts and overall metabolic health.