The largest weight I experienced in the service was Sapi plates and Ammo. Those are two things you definitely don't want to leave out, though it wasn't entirely uncommon for people to leave out plates when deployed, leading to forced inspections before movements.
I remember a kid putting a laptop in his flak jacket in place of a sapi plate...to watch movies on post or something. LCPL shenanigans.
I often ditched as much gear as I could. Sometimes it bit me in the ass though...one time in training we had to build entrenchments, but I'd left my e-tool behind. There's an old saying, "Pack light, freeze at night." I often chose to freeze. Infantry is not a comfortable life!
Sometimes you end up freezing anyway - I remember one time on a field op we settled down for the night, and there was freezing rain out. We put a tarp in the dark over where we slept, and got greeted a few hours later with a flood of rain over all of us. It rained so much that our tarp gave way to the rain.