17/08/2026
The post-lunch dip is a circadian phenomenon, not a pathology.
Core body temperature and subjective alertness both fall in a predictable trough roughly seven to nine hours after waking, independent of what you ate. It was present in adolescence too but it was simply masked by higher baseline arousal.
Low-stimulation, sedentary tasks remove that masking, which is why the same physiology becomes conspicuous in your thirties.
Bright light exposure, movement, or a really short nap address it more reliably than additional caffeine.