Your favorite podcaster just advises you to train on an empty stomach to lose fat faster. Next, a trainer on social media insists that you should eat before a workout to see real results.
But… who’s right?
If you’re confused, you’re not alone. With fitness tips coming at you from all directions, it’s no wonder that fueling your workouts feels more complicated than it should be. But here’s the thing: your body isn’t a podcast experiment or an algorithm, it gives you signals every day.
As a registered dietitian and personal trainer, I see it all the time: people who unknowingly under-exercise in the name of weight loss or “optimization” and then wonder why they feel exhausted, stagnant, or stuck (1). And yes, these are real signs that your body may not be getting enough energy.
Let’s explain why it’s important to eat enough to exercise, how malnutrition can manifest itself, and what to look for when your body is craving more.
Why it is important to eat enough while exercising
Your body doesn’t just want calories, it needs them to support all the functions you rely on every day, from breathing and thinking to movement and training. When you exercise, your energy needs increase: your muscles use fuel to contract, your nervous system coordinates movements, and your body then works to repair and adapt (2). That’s why it’s important for both performance and recovery to consume enough calories with the right mix of nutrients.
Research in sports nutrition describes something called energy availability, or the amount of dietary energy left over for your body’s everyday processes after taking into account the energy you expend during exercise.(3) When energy intake does not keep pace with energy expenditure during exercise, your body cannot fully support things like muscle repair, hormone function, and even immune system health, which directly impacts your performance and adaptation to exercise.(1,4)
In short, eating enough isn’t just about consuming calories to reach your desired calorie count on a scale, it’s about giving your body the fuel it needs to perform, recover, and get stronger during exercise.
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Signs You’re Not Eating Enough to Fuel Your Workouts
Not sure if you’re consuming enough calories to support your workout? Check yourself and the following signs and symptoms that usually occur when you have low energy.
Low energy and persistent fatigue
Feeling constantly exhausted can be a sign that you’re not eating enough to maintain your activity level. Research shows that normal functioning can be impaired when calorie intake does not meet the increased energy demands of exercise (1,3,4). Over time, this lack of energy can leave you feeling exhausted both in and out of the gym.
In real life, this might look like having trouble staying awake during the workday, skipping workouts you normally enjoy, or giving up social plans just because you don’t have the energy left.
Slow recovery, persistent pain and/or decreased performance
protein promotes muscle regeneration (2). When you strength train or do an intense workout, tiny muscle fibers are stressed and need to be repaired. Protein provides the building blocks for this repair and growth (2). Inadequate protein intake can lead to slower recovery and persistent muscle soreness, making your next workout feel more strenuous than it should (1,3,4).
Calories, especially from carbohydrates, increase your performance (2). Carbohydrates Replenish your muscle glycogen, which is the main energy your muscles rely on during most workouts (2). When glycogen stores are low, your strength, endurance, and overall exercise intensity can be affected (1,3,4). Consuming enough carbohydrates will allow you to train harder, recover faster, and get the most out of every session.
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Physical symptoms you may not expect
When your calorie intake is insufficient to meet the energy needs of daily life plus exercise, your body goes into “survival mode” and begins to downregulate systems such as metabolism and hormone production to conserve energy (1,3,4). This reaction can increase your risk of illness or injury because your immune system is weakened by the low energy intake (1).
Persistently low energy availability, the gap between what you eat and what your body uses, is associated with a syndrome known as relative energy deficiency in exercise (RED-S) (1,5). This condition affects metabolism and hormonal balance, as well as training results (1,5). RED-S can also manifest in changes in bone health, with a higher risk of stress fractures as well as effects on reproductive health, particularly in women who miss their periods (1).
Use MyFitnessPal to support your nutrition and fitness goals
MyFitnessPal helps you stay on track with both your nutrition and fitness goals, and of course, proper fueling is an important part of that. For example, did you know that you can adjust your activity level in your profile to help the app better estimate your daily calorie needs? And you can customize your nutrient goals – making it easier to meet your energy needs whether you’re training hard or taking a rest day. By entering your personal goals, whether it’s getting enough protein, hitting your calorie goal, or staying hydrated, you can track your progress week by week and make healthy habits a regular part of your routine.
Learn how to update yours Nutrient requirements in MyFitnessPal
And don’t forget your personalized nutrition overview. The more consistent you Log your foodthe more insightful this breakdown becomes. It makes it easy for you to identify trends over time, identify where adjustments may be needed, and help you advance your training and recovery in a way that meets your goals.
Explore My weekly report in the app
Conclusion
Ultimately, there is no one-size-fits-all answer to pre- or post-workout nutrition. Many may have an opinion, but your body is the best guide. Paying attention to your well-being, recovering well and performing consistently are the clearest signs that you are properly energizing.
Eating enough calories and getting the right balance of nutrients isn’t just about weight or appearance, it’s also about giving your body the energy it needs to perform, recover and adapt to your workout. Signs such as persistent fatigue, slow recovery, persistent pain, or unexpected physical symptoms may indicate that it is time to reconsider your nutritional strategy (1,3,4). MyFitnessPal nutritionist Brookell White explains, “To achieve your goals, it’s important to properly fuel your body. Think of it as a form of self-care that will help you train smarter, recover faster, and feel better.”
The good news? Tools like MyFitnessPal Make it easier than ever to track your diet. By adjusting your activity levels, tracking habits, and monitoring your macronutrients, you can help your body get the nutrients it needs, both for your workouts and in everyday life.
The post How do I know if I’m eating enough to support my training? appeared first MyFitnessPal Blog.
