I've posted a kit list as you may have read.
I have got my full winter walking kit for a 3 day trip down to 12kg including food and 2l of water.
As others have said, I've done so by getting rid of things I don't use, or can double up.
Getting lighter gear, mostly, down bag, lighter tent, down camp wear, LW rucksacks and planning meals so I don't take much more than I need.
I do take a few extras, food wise, as can get a bit boring eating same thing every day.
I take dehydrated food, of different flavours, so not eating the same one each day. I also take the likes of mini salami/pepperami to add to meal.
Sometimes if I get Lidl's own brand rice meals, they are more than I can eat at night. I'll keep the rest for breakfast, with maybe some cheese and oatcakes.