Yes, you read that headline right. Many people begin exercising with the goal of improving their health, building strength, or losing weight. At the same time, they often try to cut calories as much as possible in an effort to speed up results.
While this approach may seem logical, consistently underfueling your body can actually work against your goals, especially when exercise demands increase.
As a dietitian, one of the most common patterns I see is individuals working out regularly but not eating enough to properly support their activity level. Over time, this can negatively affect energy levels, recovery, performance, metabolism, and even body composition.
What Does Underfueling Mean?
Underfueling occurs when your body is not receiving enough energy, calories, and nutrients to support both daily functions and physical activity. This does not necessarily mean someone is starving. In many cases, people are eating regularly but still falling short of what their body actually needs.
This is especially common among people trying to lose weight while increasing exercise. They may skip meals, avoid carbohydrates, delay eating after workouts, or rely on very low-calorie meal plans while expecting their body to perform well during training.
The body, however, interprets this differently. When energy intake is consistently too low, the body begins conserving energy rather than optimizing performance and recovery.
Common Signs You May Not Be Eating Enough
Underfueling can show up in several ways, many of which are often mistaken for normal side effects of exercise or dieting. For some individuals, underfueling can also disrupt hormones, impact menstrual cycles, and increase stress.
Some common signs you are not eating enough include:
- Fatigue or low energy throughout the day
- Feeling weak during workouts
- Dizziness or lightheadedness
- Increased cravings or overeating later in the day
- Difficulty recovering between workouts
- Poor sleep
- Irritability or mood changes
- Frequent illness or injury
- Loss of muscle mass
- Weight loss plateaus despite exercising consistently
Why Eating Too Little Can Stall Progress
Many people assume that eating less always leads to faster weight loss. In reality, chronic underfueling can make progress more difficult.
When your body does not receive adequate energy:
- Workout intensity and performance decline
- Recovery slows down
- Muscle repair and growth are impaired
- Hunger and cravings often increase
- Daily movement and energy expenditure may unconsciously decrease
Additionally, inadequate protein and carbohydrate intake can make it harder to preserve lean muscle mass. Since muscle tissue plays an important role in metabolism, losing muscle may ultimately reduce the number of calories your body burns at rest.
The goal should not simply be to eat less and exercise more. Sustainable progress comes from appropriately fueling your body while creating a realistic and moderate calorie deficit when weight loss is desired.
The Importance of Carbohydrates
Carbs are often the first nutrient people restrict when trying to lose weight, yet they are the body’s preferred source of energy during exercise.
Carbs are stored in the muscles as glycogen, which helps power workouts, especially strength training, running, cycling, high-intensity exercise, and longer workouts. Without adequate carb intake, workouts can feel significantly harder, and recovery may suffer.
Low carb intake may contribute to early fatigue during exercise, reduced endurance, increased soreness, and difficulty building or maintaining muscle.
Choosing quality complex carb sources such as fruit, oats, rice, potatoes, whole grain breads, pasta, beans, and dairy products can help support both performance and recovery.
Repeat after me: carbohydrates are not the enemy. They are fuel.
What Proper Pre-Workout Nutrition Looks Like
A balanced pre-workout meal or snack helps provide energy and improve performance. Ideally, this includes carbohydrates for fuel and some protein for muscle support.
Timing matters, too. Larger meals are typically best eaten 2 to 3 hours before exercise, while smaller snacks may work well 30 to 60 minutes beforehand. Skipping food before a workout may leave you feeling sluggish, weak, or unable to perform at your usual level.
Here are some examples of pre-workout options:
| 2 to 3 Hours Pre-Workout | 30 to 60 Minutes Pre-Workout |
|---|---|
| Greek yogurt and berries | Apple and string cheese |
| Oatmeal and peanut butter | Banana and peanut butter |
| 1 to 2 eggs and toast | Applesauce pouch |
| Baked chicken and rice | Granola bar |
| Peanut butter and jelly sandwich | 8 to 12 ounces of a sports drink |
What Proper Post-Workout Nutrition Looks Like
After exercise, the body needs nutrients to replenish energy stores and repair muscle tissue.
Many people focus only on protein after workouts, but carbohydrates are equally important for recovery. Post-workout nutrition should ideally include protein to support muscle recovery, quality carbohydrates to restore glycogen stores, and fluids and electrolytes for hydration.
Don’t forget about your next meal. You can time your next meal to also serve as your post-workout fuel option.
Here are some examples of balanced post-workout meals or snacks:
- Greek yogurt with fruit and granola
- Turkey sandwich and fruit
- Cottage cheese with peaches and cinnamon
- Tuna with crackers and baby carrots
- 1 scoop of Regenerate mixed in 8 ounces of milk or a milk alternative with an apple
Fueling Your Body Supports Better Results
Exercise places stress on the body and requires proper recovery. Optimizing your nutrition allows your body to adapt, recover, build strength, and perform effectively.
If your workouts constantly leave you exhausted, sore, or feeling depleted, eating more strategically may actually help you see better results, not worse ones.
Rather than viewing food as something to earn or minimize, it can be helpful to think of nutrition as a tool that supports your goals. Adequate fueling improves energy, workout quality, recovery, muscle preservation, and long-term sustainability.
In many cases, the issue is not that someone is exercising too little. It’s that their body is trying to do too much with too little fuel.
Here are a few resources for simple meal prep ideas:
Work With a Registered Dietitian
Want to optimize your nutrition to fuel your workouts, improve recovery, and avoid underfueling? Partnering with a Registered Dietitian can provide personalized support tailored to your goals, lifestyle, and training needs.
Plus, many insurance plans offer coverage for nutrition counseling, making it more accessible than you might think.
To learn more or schedule a visit, email us at dietitians@mend.me or reach out →
This article was written by Katie Frushour, MS, RD, CSSD, a dietitian at Mend.
