The conventional “wisdom” about weight and exercise ignores important evolutionary patterns. For starters humans evolved to interpret stress triggers that include physical exertion or anxiety and fear as a signal for the body to switch into the self-preservation mode and start hording fat. The release of Cortisol by the Adrenaline glands negates the caloric loss from an exercise and has the potential to disrupt sleep. So contrary to a physical exhaustion after a hectic day people have trouble falling asleep. This again would be an obvious evolutionary protective adaptation to danger.
Everyone who ever fasted knows that a fast sharpens your mind. This again is an evolutionary trigger. When a human body gets a starvation signal it preferentially partitions energy to brain. The body knows that your survival depends on the alert concentration for hunting and gathering.
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