Well... Why don't you go sprint several marathons, fight a hundred zombies, dig several hundred cubic meters of soil and stone, chop a few dozen trees down, jump all over the place all while recovering from grievous injuries all in one day and see how hungry
You feel after all that.
In different phrasing, Hunger decay is actually pretty slow. But all your activity from sprinting to jumping to swinging tools to climbing, to swimming, to recovering health all consumes hunger bit by bit- The more active you are, the faster your hunger goes down; Which, in all honesty, is pretty accurate. The player can singlehandedly achieve more by themselves in a single game day than a dozen strong burly men can in a work week; So it's completely fair imo for a commensurate amount of caloric intake to be matched against your tireless physique.
The most notable alternative to all your actions consuming hunger is a hard daily limit on how much activity you can have balanced...
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