An empty meter costs you healing, not health
This is the question people actually arrive with, so it goes first: starving does not kill you. Emma and Koo each carry a hunger meter — a small circle with a grain icon beside the health bar — and it falls as you travel and fight. While it has anything in it, that character slowly recovers HP on their own. When it empties, the recovery stops. Nothing else happens. NerdsChalk puts it in the sentence this page would have written if it had got there first: hunger is a recovery limiter, not an instant death timer.
- Two meters, not one. Feeding Emma does nothing for Koo, and his treats are a separate item in the same pack.
- The recovery is passive and it is free. There is no cost to being fed beyond remembering to do it.
- It only pays out between fights — see below, which is the detail that decides when this matters.
It only works out of combat, which is what decides when it matters
NerdsChalk is the only source that pins this down, and it changes the advice completely: the recovery is what happens outside combat, while you are exploring between encounters. So an empty meter is expensive on a long exploration run — the chip damage from trash mobs stops healing back and you arrive at the next fight already down — and close to irrelevant during a boss, where you were never regenerating anyway. If you are dying to a boss, hunger is not what is wrong. If you are arriving at bosses at 60% health, it probably is.
The one thing the guides disagree about
Every source agrees an empty meter stops recovery. Only Game Rant says the rate scales with how full the meter is — "the more full they are, the more HP they will gradually recover". ScreenRant describes the same system as a threshold and never mentions a slope; NerdsChalk does the same. Nobody publishes a number on either side. This matters practically: if the threshold reading is right, topping up from a quarter full is wasted effort and the only state worth avoiding is empty. If Game Rant is right, a full meter is doing real work. Until somebody measures it, the safe play is the cheap one — the pack refills for free, so keep it topped and the question never comes up.
The fight where a full meter is doing the most work
AppMedia, writing in Japanese, makes a connection the English guides do not: keep 満腹度 topped up because the continuous HP recovery blunts the slip damage a status effect does over time. That is tactical advice from a competitor rather than a first-party statement about damage numbers, and it is worth what that is worth — but it is the one situation where the two systems interact, and it explains why the Japanese portals treat hunger as a combat topic while the English ones file it under survival. If you are bleeding out from poison or acid on the way back to a camp, a fed character is losing that race more slowly.
The resource is free, so forgetting is the only failure
Every time you leave the Cleanse Walker your battle pack refills with field rations, hard candy and Koo treats. Open it with down on the d-pad, or use View Pack at a camp. Field Rations, Grilled Meat and Grilled Fish are the cleanest options because their own item text names both meters, and fish come out of any river and cook on the spot when the pack runs dry. There is no economy here to manage and nothing to ration — which is exactly why the meter catches people out, because a system with no cost attached is the one you stop looking at.