Have you ever found yourself slumped on the sofa at the end of a mentally exhausting day, convinced your brain must be running on empty? New research suggests that feeling mentally drained may have surprisingly little to do with how much energy your brain actually uses — and may be rooted in stress rather than any hard limit of cerebral power.
According to a comprehensive new analysis led by neuroscientists at Monash University, the human brain consumes almost the same amount of energy whether you’re intensely engaged in mental problem-solving or simply daydreaming. “The metabolic increase is about 5% when comparing resting and active states,” the researchers concluded, challenging a widely held assumption that tough cognitive work significantly depletes our fuel reserves. The study, published in June 2025 and widely discussed in the global science press, upends popular beliefs about what causes mental fatigue and carries profound implications for how Thais approach work, study, and daily life (zmescience.com).
For Thai readers — whether university students facing relentless exam periods, office workers pushing through data-laden projects, or elders grappling with age-related changes in memory — these new insights are both timely and relevant. Understanding the true sources of mental tiredness could reshape health advice, education strategies, and even national policymaking around workplace wellbeing.
Beneath the surface, your brain — which constitutes only 2% of your total body weight — uses an estimated 20% of your body’s daily energy budget. This amounts to about 0.3 kilowatt hours per day, a figure over 100 times greater than your mobile phone’s power consumption. The majority of this energy supports continuous “housekeeping” duties: neurons maintain delicate electrical gradients (called membrane potentials) that keep them ready to fire, even when you are staring at a flickering TV screen after hours of meetings or school classes.
Scientists long attributed post-exam zombification or the fogginess after a marathon business negotiation to a dramatic spike in the brain’s energy demands. But the Monash University-led analysis, which reviewed decades of brain imaging studies, found that even rigorous mental tasks — from memorizing vocabulary to strategizing complex chess moves — increase energy use only slightly and only in specific brain areas. For instance, tackling a logic puzzle will cause a regional uptick in glucose consumption in the prefrontal cortex, but other regions simultaneously dial down their activity, maintaining a careful energetic balance.
“This isn’t a case of the whole brain lighting up like a light bulb,” one neuroscientist from Weill Cornell Medicine–Qatar commented in a recent interview with Quanta Magazine. “Even difficult thinking draws just a modest boost in fuel, and only in certain networks.” Thai cognitive scientists and neurologists have echoed these results in interviews with national media, highlighting that fatigue does not reflect a depleted supply of brain energy, but is more likely a byproduct of evolved biological caution and emotional regulation.
So what’s behind the feeling of mental “energy drain” so familiar to Thai students or knowledge workers? Recent research points to stress: the physiological and psychological arousal that accompanies high-stakes tasks often causes mental weariness. Frustrations, uncertainty about outcomes, and pressure to perform — often amplified in Thailand’s competitive educational and business environments — trigger the sympathetic nervous system, flooding the body with cortisol and other stress hormones. “You’re not actually running out of calories in your brain,” said a neuroscientist quoted in the study, “but your evolutionary biology is prompting you to stop before the costs of persevering outweigh the benefits.”
Intriguingly, the research also highlights the astonishing efficiency of the human brain. Running all its daily responsibilities — controlling your heartbeat, integrating complex sensory information, planning future actions — takes just 17 watts of power, equivalent to a standard dim light bulb. By comparison, supercomputers simulating equivalent tasks consume several megawatts, underscoring just how finely tuned the Thai people’s central nervous system is for conserving resources.
Historically, this thriftiness evolved for survival. Our ancestors faced an unpredictable environment and frequent food shortages; their nervous systems, and by inheritance ours, became systems that are stingy with every extra percentage point of energy. For a modern Thai, this means the brain’s design is still guided by caution over wastefulness, even though food and energy are more readily available today.
To measure energy use in the living brain, researchers rely on advanced PET scans and fMRI imaging. These tools track how the brain’s regions handle glucose and oxygen at rest versus during mentally demanding activities. The data are clear: while active thought does register a local increase in energy consumption, it’s a minor adjustment, not a wholesale surge.
Moreover, there’s little evidence that “brain burnout” is caused by metabolic gasping. Instead, the fatigue that follows marathon revision sessions or hours of online business meetings is likely the result of stress responses and the brain’s finely tuned regulatory mechanisms urging us to take breaks. One theory suggests that mental fatigue is a kind of safety check, nudging us to stop before real damage can occur — a biological insurance policy that should not be ignored.
For older Thais and those living with diabetes, these findings are especially relevant. The research notes that as we age, glucose metabolism slows, especially in areas crucial to memory and executive function. Insulin resistance, prevalent in an aging Thai population, can impair glucose delivery to the brain — eventually impacting cognition and increasing the risk for neurodegenerative diseases such as Alzheimer’s. This underscores the importance of maintaining metabolic health (through diet, physical exercise, and disease prevention) as a central strategy for preserving cognitive function into old age.
In Thailand, where the prevalence of diabetes and metabolic syndrome is rising quickly, public health experts are already advocating for nation-wide campaigns about “brain fueling” through balanced nutrition and regular physical activity (World Health Organization). The Monash findings offer scientific backup for these efforts — but also suggest a new focus: managing psychological stressors within schools, offices, and homes could be just as important as dietary guidelines.
The Thai education system, vocally critiqued in recent years for its frequent high-stress testing and “rote” learning methods, might also benefit from a rethink. If student fatigue stems less from “overthinking” and more from performance anxiety and emotional stress, then interventions such as mindfulness training, better counseling, and reduced exam pressures could be more effective than simply adjusting study loads. Progressive Thai schools are already integrating wellness breaks and attention to emotional intelligence, reflecting the evolving science.
A wider look at Thai society reveals that many modern lifestyle factors — long hours in the office, high expectations in school, digital multitasking — can drive stress and mental fatigue. The Buddhist concept of “santiphap” (inner serenity and equilibrium) aligns closely with neuroscientific recommendations for regular rest and resetting. Traditional Thai practices like meditation, mindful eating, and respectful social interactions foster conditions that help regulate the stress response and, by extension, the feeling of mental exhaustion.
Looking to the future, experts believe technology will offer deeper glimpses into the brain’s operations, but the fundamental conclusion will likely remain unchanged: your brain is always on, always working, and overwhelmingly energy-efficient. Instead of worrying about running out of mental fuel, Thais may be better served by finding healthy ways to reduce stress, balance work and rest, and cultivate inner calm.
Practical recommendations for Thais, drawn from the latest research and traditional wisdom, include: prioritizing regular physical activity and a diet rich in whole foods to sustain metabolic health; fostering open discussion about emotional wellbeing at work and school; incorporating mindfulness and relaxation techniques into daily routines; and, crucially, acknowledging the limits of willpower when stress levels run high. By blending cutting-edge science with time-honored Thai cultural values, everyone can take concrete steps toward lasting brain health and resilience.
As global research and Thai experience converge, it’s clearer than ever: feeling mentally tired isn’t proof of running out of brain energy — it’s your body and mind’s way of keeping you safe in a fast-moving world. By respecting these signals and addressing root causes such as chronic stress, Thailand can continue to foster a smarter, healthier, and more balanced society.
Sources: ZME Science, Quanta Magazine, The Conversation, World Health Organization – Thailand