In case you have not seen it, I recommend a good book from the Gulf War titled "Bravo Two Zero." It was written by the leader of a British SAS team that was dropped into Iraq to hunt Scud launch sites. Each man went into Iraq carrying 212 pounds. The SAS are some studly dudes. A lot of their load was water. At about 8 pounds per gallon and each man carrying several gallons, well, the weight added up pretty quickly.

Our Special Forces troops need enough food to operate for quite a while without resupply. They may need to hump in their water if it looks like there won't be much available in their ops area. They'll need to carry their basic weapons load as well as team equipment (radio, batteries, extra ammo for belt fed weapons, etc.) It all adds up pretty quickly. Fortunately, they can drop all but their web gear in an emergency and move like a bat out of hell.