Why thinking hard makes us feel tired
Intense mental effort may feel physically exhausting, but how much extra energy the brain actually uses is contested. Commenters examine a study linking cognitive fatigue to glutamate buildup in the prefrontal cortex, compare this to claims about chess grandmasters burning thousands of calories, and contrast subjective exhaustion with relatively small measured increases in metabolic demand. The thread branches into related topics such as chronic fatigue syndromes, stimulants like amphetamines and caffeine, and practical strategies (diet, exercise, sleep) for improving cognitive endurance.
Access to article and original study
- Several comments share archive links to bypass the paywall.
- Others link directly to the underlying Cell paper, noting it is now open-access.
- One commenter highlights the paper’s own caveat that results are correlational, not proof that glutamate accumulation causes cognitive fatigue.
Glutamate, brain metabolism, and analogies
- A question compares glutamate buildup in neurons to lactic acid in muscles; replies say this analogy is inaccurate, and that lactic-acid explanations of muscle fatigue are themselves oversimplified or mythologized.
- Some discussion notes the brain’s high oxygen and energy demands per cell and its role as the body’s “most expensive” organ.
Mental effort, fatigue, and subjective experience
- Several people distinguish “feeling tired” from objectively “being tired”; one answer frames the former as an indicator of the latter.
- Multiple anecdotes: intense cognitive work (e.g., hard problems, altitude, ADHD tests) feels disproportionately exhausting compared to the apparent physical load.
Chess, weight loss, and calories
- Articles are cited claiming chess grandmasters lose significant weight during tournaments.
- Many are skeptical that “thinking hard” alone explains this, suggesting stress, reduced appetite, deliberate under-eating, water loss, and possibly stimulants.
- A paper is cited estimating only ~10% higher energy expenditure during chess by direct respiration measures, challenging extreme calorie-burn claims.
- Debate over the “3,500 kcal per pound of fat” rule and whether tournament weight loss must be fat vs. water.
Cognitive tasks as “torture”
- The study’s n-back–style task is widely described as tedious and mentally draining.
- People relate it to ADHD screenings, dual n-back, and fast-paced card games that stress working memory, noting how quickly focus collapses without strong intrinsic reward.
Stimulants, ADHD, and concentration
- Extended discussion of amphetamines and caffeine:
- Some say stimulants help sustain effort and “borrow energy from the future.”
- Others stress that in non-ADHD brains they may not improve quality of thinking, only persistence.
- Debate around how strong caffeine is as a psychoactive drug, including a side argument about toxicity vs. psychoactive potency.
- Foot tapping and similar “stimming” behaviors are discussed as common, sometimes linked to ADHD, anxiety, or just habit.
Chronic fatigue, glutamate, and self-treatment
- A long subthread covers chronic fatigue–like symptoms: suspected links to glutamate buildup, infections (Lyme, fungal, parasitic), mast-cell issues, and gut problems.
- Various self-devised regimens are described: N-acetylcysteine, niacinamide, keto, pyruvate, sauna/cold exposure, carnivore-like diets, and extensive supplement experimentation.
- Others caution that chronic fatigue is multifactorial, diagnosis is hard, and there is skepticism about specific internet treatment protocols and qualifications.
Improving cognitive endurance
- Some ask how to train “thinking endurance”; concrete answers are limited.
- A few note that regular physical exercise, adequate food, and good general health noticeably reduce subjective mental fatigue.