The Brain’s Energy Budget: Why You’re Not Lazy, You’re Overdrawn
- Dr. CK Bray
- Sep 22
- 3 min read
Ever hit that 3 PM wall and wonder why you can’t focus? You’re not lazy. You’re not unmotivated. You’re cognitively overdrawn. Your brain, though it makes up only 2 percent of your body weight, uses up about 20 percent of your daily energy. Most of that energy is spent by the prefrontal cortex, the part of the brain responsible for decision making, planning, focus, and emotional control. Unlike muscles, your brain doesn’t store fuel. When it runs low, the first thing to go is not your ability to walk or talk, but your ability to think clearly, manage emotions, and resist distractions.
Think of your brain like a checking account. Every decision, distraction, and task acts like a withdrawal, slowly draining your mental balance. If you don’t make deposits, through breaks, rest, movement, or nourishment, you enter a state of cognitive overdraft. That foggy, irritable, or unmotivated feeling? It’s not a personal flaw. It’s biology doing its job.
Many people also fall victim to decision fatigue and task switching without realizing the cost. Every single decision, even small ones like what to eat for lunch or how to respond to a Slack message, activates energy-intensive circuits in the brain. When you add context switching into the mix, it becomes even more costly. Every time you shift from one task to another, your brain needs time to reset and refocus. Research from the University of California, Irvine, found that it can take up to 23 minutes to regain full focus after switching tasks. It’s like trying to sprint while tying your shoes mid-stride. You’re not moving faster, just burning out faster.
The brain also works in cycles known as ultradian rhythms. These are natural patterns of high energy followed by a need for recovery, lasting about 90 to 120 minutes. Ignoring these rhythms and pushing through can leave you feeling tired, scattered, or wired without being productive. Neuroscientist Andrew Huberman recommends short intentional breaks, called Non Sleep Deep Rest practices, as a way to reset attention and energy. This might include deep breathing, a brief body scan, or simply closing your eyes and visualizing success before your next meeting. Even just a few minutes of strategic rest can refresh your mental clarity and emotional regulation without needing caffeine.
To stay mentally strong throughout the day, you have to make regular energy deposits. Movement, novelty, social connection, and quality fuel are all proven ways to refuel your brain. Physical activity stimulates the release of brain derived neurotrophic factor, which protects neurons and enhances learning. Positive social interaction boosts oxytocin and lowers stress hormones like cortisol. New and engaging experiences activate your brain’s reward system, creating motivation and alertness. And of course, basic habits like sleep, hydration, and nutrition give your brain the raw material it needs to perform well.
To apply this in a real workplace setting, start by changing how you measure productivity. Ask not just how much got done, but what kind of energy was brought to the most important work. Consider blocking off 90-minute periods for focused work, where notifications are silenced and decisions are minimized. Encourage walking meetings or begin team calls with a quick personal story to create novelty and human connection. Provide healthy snacks and hydration stations. And challenge your team to log their mental energy for one workday. Ask them to reflect on what drained them, what refueled them, and when they felt sharp versus when they hit a wall. Once people can see how their brain energy fluctuates throughout the day, they can start to use it with intention rather than exhaustion.
Your brain is powerful, but it is not limitless. By understanding and respecting its energy budget, you can do better work, with less strain and more fulfillment.
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Header image by Wayhomestudio Freepik
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