I hate to be the one to bring reality into a fantasy game...
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Back to the fantasy game. A good idea posted earlier was dropping the pack when they went into combat; just common sense. Here's also something I'm going to try with my group. Work with your players on a 'basic load'; the pack that everyone is carrying that they drop going into combat. Bedroll, rations, mess kit, waterskin, etc. Figure out that weight and then don't worry about it. Assume that load is only carried part of the time, since they're going to take it off when they take a short rest as well. All the other stuff they consider they 'need' for combat is what is important to track, anyway; armor, weapons, ammunition, flasks of oil, etc. That should cut down on some of the bookkeeping.
I'd add treasure to what's dropped in combat. If you're carrying a sack of coins, you're not going to hold onto that going into combat. It gets dropped at the first sign of a threat (unless they're surprised).