Thinking hard burns almost no calories but destroys your next workout

Caffeine and Pre‑Workout Dosing

• Several commenters note that the article’s suggested 3–6 mg/kg caffeine is very high; for some it would cause jitters and anxiety, others see it as normal and point to evidence of benefits at those levels.
• Pre‑workout products often include ~300 mg caffeine; some mention yohimbe side effects.

Creatine: Doses, Effects, and Side‑Effects

• Multiple people expected creatine to be discussed given its ATP link and report improved mental endurance and reduced sugar cravings.
• Typical daily doses mentioned: 5 g (most evidence), 7.5 g, and 10–15 g (especially for non‑meat eaters).
• There’s debate whether higher doses are needed for brain effects; some studies used very large single doses and note the blood‑brain barrier and muscle “topping up” first.
• Reported downsides include poor sleep (night urination), GI issues, and constipation.
• Some argue meat eaters gain less cognitive benefit; others say the dietary gap isn’t that large.

Brain Energy Use vs AI Systems

• Several answers to why brains do complex work on little energy: very different architecture, sparse spiking events, analog timing, and heavy “idle” cost with relatively small incremental cost for extra firing.
• Comparisons are made to emulating older hardware: simulating biological-like systems on digital hardware is inherently expensive.

Exercise, Calories, and the “Exercise Paradox”

• Long subthread on how much exercise “really” burns.
• Some insist an hour of intense running or cycling can burn ~800 kcal; others question measurement accuracy and emphasize that wearables rely on rough regressions.
• Many stress that most daily energy goes to basal metabolism and thermic effect of food; exercise is a minority share for typical people.
• Discussion of research on constrained total energy expenditure and the “exercise paradox” (high-activity populations showing similar daily burn to low-activity ones after adaptation).
• Consensus trend: exercise clearly uses energy and has major health benefits, but diet is usually more impactful for weight loss than “earning back” calories via workouts.

VO2 Max App and Wearables Skepticism

• Criticism that the advertised product markets Apple Watch VO2 max as if it were a true measurement, when it’s an estimation based on biomarkers and is notably inaccurate compared with lab calorimetry.
• Agreement that reliable VO2 max still requires gas‑exchange equipment; some niche devices exist but are expensive.

Mental vs Physical Fatigue and Adenosine/Glutamate

• Many users report that heavy cognitive work degrades workout quality, and conversely that hard workouts make subsequent deep work harder, feeling like a shared “willpower/energy” pool.
• The adenosine explanation in the article resonates with several commenters; another cites a glutamate‑buildup study as a similar mechanism.
• Some argue glucose is a poor proxy for “thinking cost” and suspect delayed metabolic effects (e.g., during sleep).

Life Logistics: Scheduling Exercise vs Cognitive Work

• Some simply avoid the problem by training in the morning; others find morning workouts wreck their workday focus and prefer evenings, but worry about sleep impacts.
• Advice offered: adjust intensity (more zone‑2, less all‑out), move workouts earlier in the evening, and prioritize diet over “hard” workouts for weight loss.

AI‑Generated Writing and Content Marketing

• Many readers feel the post is AI‑generated or AI‑edited: cliched transitions, uniform sentence lengths, dramatic “kicker” lines, and at least one hallucinated citation.
• Some argue this style already existed in human content marketing; others say heavy AI use is obvious and makes the piece feel like generic “content marketing slop.”