Have personally done 14 days without resupply while doing a circuit around the coast of stewart island in nz (pic related). Initial pack weight was around 18kg with about 500g food per day. Water weight wasn't an issue - never had to carry more than a litre. Didn't try fishing but had oysters a few times.
Food type and quantity is down to personal preference and is something that comes with experience.>>1696365>>1696155
Caloric consumption is largely irrelevant in this context. On longer trips, it makes sense to carry less food than is actually required. Your body has stores of fat for this very purpose. Maintaining adequate protein intake is arguably more important.
Now, regarding OP's original question, I would say that without accounting for hunting/foraging/fishing, a fit and adequately supplied adult male should be able to walk for around 3-4 weeks without resupply. Not many places on earth which are sparsely populated enough for a resupply interval of this length to be necessary though...