If you’ve ever found yourself staring blankly at your computer screen at 2:00 PM – battling intense brain fog, a midday slump, and a sudden wave of irritability, even when you feel like you’ve been “eating healthy” – you are not alone.
For some people, symptoms like low energy, brain fog, or irritability may be related to under-fueling, including not getting enough carbohydrates. In a culture where diet messaging often teaches people to fear carbohydrates, it is easy to forget an important biological fact: carbohydrates break down into glucose, one of the brain’s key sources of energy.
The brain may be small, but it is an incredibly hard-working organ that requires a significant amount of energy to function. Today, we will explore exactly how your mind uses this energy and how to keep it happily fueled – without any fear, shame, or rigid rules.
What Are Carbs, Anyway?
Carbohydrates are one of the body’s three main macronutrients, sitting right alongside protein and fats. They are a broad, diverse food group found in many nourishing options – ranging from grains and fruits to vegetables, sturdy potatoes, and beans.
When we eat carbohydrate-rich foods, our digestive system breaks them down into a simple sugar known as glucose. This glucose then enters the bloodstream, acting like a delivery system that brings essential energy directly to our cells.
How Your Brain Uses Glucose
The brain is one of the most energy-demanding organs in the body. Although it makes up only about 2% of your total body weight, your brain consumes roughly 20% of your body’s daily energy.
Unlike other tissues that have substantial energy reserves, the brain relies on a continuous supply of glucose from the bloodstream. This high demand for energy comes from the brain’s constant need to power essential background processes like:
- Managing cell-to-cell communication
- Supporting brain processes involved in communication and mood regulation
- Supporting cognitive functions like focus, memory, and emotional regulation
Think of glucose as the high-quality fuel that keeps your internal computer running smoothly. Without it, the system may naturally start to lag!

What Happens When Intake is Too Low?
Skipping meals, having high energy needs, or following a restrictive low-carbohydrate diet may make it harder for some people to meet their overall fuel needs.
When carbohydrate intake is very low, the body must adapt by using alternative sources of energy. Though the body is incredibly resilient and can adapt to some extent, some people experience noticeable symptoms when their glucose supply dips.
Take a Moment to Reflect: Is Your Brain Trying to Tell You Something?
To see if your brain might be running low on its favorite fuel, ask yourself if you regularly experience any of these common signs:
- Do you experience midday brain fog? You might find yourself staring at a screen or having a hard time focusing on tasks that usually come easily.
- Are frequent headaches or afternoon slumps part of your routine? This may happen for some people when overall energy intake is inconsistent or too low.
- Do you feel unusually irritable or “hangry”? Your mood is deeply tied to energy availability, and a sudden drop can leave you feeling easily frustrated.
- Are you battling overall cognitive fatigue? This is the distinct feeling of being completely mentally exhausted, even early in the day.
While these symptoms can have many causes, including sleep, stress, hydration, medical conditions, medications, and overall eating patterns, if they tend to show up after skipping meals, going long periods without food, or intentionally restricting carbohydrates, under-fueling may be one factor worth exploring.
Keeping Your Mind Fueled and Happy
Properly fueling your body does not have to be a stressful battle. Rather than viewing carbohydrates as something to avoid, it can be helpful to view them as a vital source of energy that supports both our body and mind. Carbohydrates are not the enemy, they are one of the many ways we nourish concentration, energy, exercise performance, and overall daily functioning.
To shift away from rigid food rules and instead build a steady, reliable fuel stream for your brain, try focusing on these practical steps:
- Prioritize Consistency: Eating regular meals and snacks throughout the day provides your brain with a predictable stream of energy, reducing large dips in hunger or energy. This might look like eating breakfast before a busy morning, packing an afternoon snack, or avoiding long gaps between meals when possible.
- Aim for Variety: Celebrate different types of carbohydrates! Try pairing fiber-rich carbs with a protein or fat for sustained, long-lasting fullness and focus. Examples include oatmeal with Greek yogurt, whole grain toast with eggs or avocado, beans and vegetables with rice or quinoa, crackers with cheese or hummus, or fruit with peanut butter.
- Listen to Your Body: Notice how you feel on days you adequately fuel your body versus days you might be unintentionally running on empty. Pay attention to patterns in your energy, mood, focus, hunger, and ability to get through your day.
- Filter the Noise: Actively challenge the restrictive “good food vs. bad food” messaging you see on social media. Instead of asking, “Is this food good or bad?” try asking, “What does this food help me do?” or “How can this fit into a balanced pattern that supports my body?”
When looking to properly fuel your body, it is important to note that carbohydrate needs are different for everyone and can vary based on factors like your activity level, age, health history, appetite, and personal goals. A registered dietitian can help you determine the right amount and types of carbohydrates for your unique needs and create a realistic eating plan that supports your energy, brain function, overall health, and lifestyle.

Ready to Find Your Balance?
Carbohydrates do far more than simply fill a plate. They provide glucose, an important source of energy that helps support focus, memory, mood, and daily functioning. Rather than fearing carbohydrates, it can be helpful to think of them as one part of a balanced eating pattern that supports both your brain and body.
If you’ve been struggling with low energy, poor focus, headaches, or brain fog, it may be worth looking at your overall eating pattern, including whether you are eating enough and including carbohydrates regularly.
If you’d like professional, nonjudgmental support with energy, meal balance, or incorporating carbohydrates in a way that works for you, our dietitians are here to help!
Resources:
Arshad, M. T., S. Maqsood, R. Altalhi, et al. 2025. “Role of Dietary Carbohydrates in Cognitive Function: A Review.” Food Science & Nutrition 13, no. 7: e70516. https://doi.org/10.1002/fsn3.70516.
Koepsell, H. Glucose transporters in brain in health and disease. Pflugers Arch – Eur J Physiol 472, 1299–1343 (2020). https://doi.org/10.1007/s00424-020-02441-x
Mergenthaler, P., Lindauer, U., Dienel, G. A., & Meisel, A. (2013). Sugar for the brain: the Role of Glucose in Physiological and Pathological Brain Function. Trends in Neurosciences, 36(10), 587–597. https://doi.org/10.1016/j.tins.2013.07.001
Peters R, White D, Cleeland C, Scholey A. Fuel for Thought? A Systematic Review of Neuroimaging Studies into Glucose Enhancement of Cognitive Performance. Neuropsychol Rev. 2020 Jun;30(2):234-250. https://doi.org/10.1007/s11065-020-09431-x
Smith, M. A., Riby, L. M., Eekelen, J. A. M. van, & Foster, J. K. (2011). Glucose enhancement of human memory: A comprehensive research review of the glucose memory facilitation effect. Neuroscience & Biobehavioral Reviews, 35(3), 770–783. https://doi.org/10.1016/j.neubiorev.2010.09.008
Zhang, S., Lachance, B. B., Mattson, M. P., & Jia, X. (2021). Glucose metabolic crosstalk and regulation in brain function and diseases. Progress in Neurobiology, 204, 102089. https://doi.org/10.1016/j.pneurobio.2021.102089
















