Another vote to keeping them. If you live in Manhattan and have no room, then ok toss. Otherwise find a closet or basement somewhere out of sight to store them especially if space is not a premium. I went from a 22W to a 16W in 2010. I did not throw anything away and then in 2014 went back to a 20/22W and I was happy I did not have to shop. I was even happier this summer when I went back to the 16W clothes that I had stored and now can wear a 14 regular. I am still not done so bought some pants and shirts at a big box for 8 -16$ each. I simply could no longer wear almost all my plus sized clothing. Some still fit my waist (I hate you IR!) but did not fit anyplace else such as in the butt)
I have purged my wardrobe of anything very worn (definitely got my money’s worth on the fat clothes) or simply yucky or torn. Everything else I have boxed up in case this keto thing does not work out. I hope it does, it has so far but I have far more space than money