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Understanding the Energy Demand of the Developing Brain

Published October 2026

Many earlier articles on this blog have talked about the overall importance of cellular energy in mental health, healthspan, and chronic inflammation. This article dives deeper into why bioenergetics, energy in living systems, are extremely different in growing children versus adults.  

Recent research has highlighted significant differences in energy expenditure between children and adults. The study, led by the evolutionary biologist Herman Pontzer at Duke University, analyzed daily metabolic rates of over 6,000 people, ages 8 days to 95 years, from 29 countries. They found that children 9 – 15 months of age use 50% more energy than adults per day. Children continue to have high metabolic rates until age 5, after which the rate of use starts slowing until age 20. 

After age 20, metabolic rates remain stable until age 60, after which they begin to decline. The study found that after age 90, daily energy consumption was about 26% lower than in middle-aged adults. 

 In this article, we discuss what happens in a growing brain, an extremely energy-intensive organ. 

Why Energy Matters So Much for a Growing Brain

A study led by biological anthropologist Chris Kuzawa at Northwestern University found that young children’s brains consume not only a stunning 43% of the body’s total energy, but also that 66% of a young child’s resting energy use goes toward the brain’s energy demands.  

Compared with the roughly 20% of resting energy in adults that goes to the brain, it is clear that a young, growing brain relies heavily on the efficient functioning of well-fueled cells. 

This is why understanding how the body makes and uses energy — at the cellular level — is a useful starting point for any conversation about a child’s brain development. A child’s brain uses the energy for the following key activities:  

  • Building neurons, synapses, and protective myelin sheaths around nerve fibers 
  • Constantly pumping ions to return to resting states for production of metabolic energy
  • Constantly rewiring and remodeling the brain for learning, language development, developing and fine-tuning motor skills, and processing social interactions
  • Cleaning up cellular waste, managing blood flow in the brain, and recycling neurotransmitters 

Meet the Mitochondria, the Foundation of Overall Health

Mitochondria are tiny organelles inside almost every cell in the body. They are often called the cell’s power generators, even though their role goes beyond creating energy; they also drive all biological functions in the body and act as cellular sentinels.

The mitochondria take the food we eat and the oxygen we breathe and convert them into a usable form of energy called ATP (adenosine triphosphate). ATP cannot be stored and are generated constantly, as needed.  

 Some interesting facts about mitochondria include:  

  • An average adult human has approximately 100,000 trillion mitochondria. All cells except red blood cells have mitochondria.
  • Mitochondria make up 25% of a cell’s volume, which translates to 1000-5000 mitochondria per cell.
  • Mitochondria in skeletal muscle, heart, liver, kidneys, and brain are not identical but differ structurally and functionally. 
  • A single cell can contain hundreds to thousands of mitochondria; organs, such as the brain and muscle cells, which need the most energy, tend to have the most.
  • Mitochondria also help regulate cell signaling, calcium balance, and the body’s antioxidant defenses — not just energy.

It is important to note that the number of mitochondria in a cell and their overall quality and function affect every single aspect of health, including immune function, physical and mental growth, sleep, focus, emotional regulation, and healing. See image below.

When the Body Faces Metabolic Obstacles

Different factors can challenge the cell’s energy system: genetics / epigenetics, nutrient availability, oxidative stress, and how efficiently the electron transport chain (ETC) runs. 

Three Dimensions of Mitochondrial Health

Mitochondrial health consists of three related but distinct things and all three must work together to reliably fuel a growing body and brain: 

  • Quantity of mitochondria – more mitochondria mean more energy for biological processes, including optimum growth and functioning in children.
  • Quality of mitochondria – better quality mitochondria results in optimum energy production 
  • Functioning of mitochondria – efficiency in converting fuel into usable energy is the third important dimension in mitochondrial health 

When all three dimensions work together, supply keeps pace with demand. The vitality picture changes when one of them falls behind. 

What Happens when Mitochondrial Health is Diminished

When energy production doesn’t keep pace with the demand, especially in high-demand tissues like the brain, the effects can show up in many different ways from one child to the next. 

Think of a child’s body as a smartphone, with mitochondria as the battery.  

Growth, focus, everyday activity, and resilience are the apps running in the background. 

When the battery is fully charged, energy is abundant, and everything runs smoothly. When it dips, the system feels it; energy fades, and recovery gets harder. 

Mitochondria are the body’s power source. The more efficient and abundant they are, the more capacity your child has to meet the demands of life, including key essentials: 

  • Sleep (The Charging Station). Sleep is when the brain does much of its maintenance, clearing waste and consolidating what was learned that day. These processes are energy intensive. 
  • Focus & Steadiness (The Filter). Paying attention means continuously filtering signals and holding information in mind. For a developing brain, filtering is metabolically expensive work. 
  • Everyday Activity (The High-Wattage Task). Running, climbing, and play draw heavily on cellular energy. Movement is also one of the body’s own signals for building new mitochondria. 

A child’s brain is one of the most energy-hungry systems in nature, and mitochondria are at the center of meeting that demand. Understanding how cells make energy gives parents, caregivers, and practitioners a shared starting point for conversations about growth and development.

To explore further, watch the replays of the BlueOakNx 2025 Symposium on Mitochondrial Health, Healthspan, and Aging.

This content is for educational purposes only and is not medical advice. Consult a healthcare professional for guidance specific to your situation.

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