"Base weight" is primarily used for the sake of comparability. By leaving out consumables, the base weight number stays the same regardless of length of trip, whether overnight or ten days. You can, of course, cut total pack weight by taking less food (or, better, more calories per ounce of food so you can take less ounces without starving), picking a route where there is a water source every mile and no need to carry water, or reducing fuel needed by taking more cold meals. Base weight, though, is where most of us do the major trimming.
Not to be forgotten, though, is the fact that your feet and knees have to carry everything on your body, whether it's your pack or the clothing you wear. In other words, skin-out weight is, in the final analysis, your most important item. Interestingly, my two most significant weight reductions in the past few years have been in skin out weight, rather than pack weight. I switched from boots to trail runners and from aluminum trekking poles to carbon fiber. Both changes significantly increased my comfort even though they had no effect on base weight!
Also, remember that your clothing system includes what you are wearing. The clothes you wear should be analyzed as part of your total clothing system to avoid duplication--or gaps.