I am not sure about discectomies as far as reflexes, it could be that if a nerve was manipulated during surgery it could be a healing thing.BUT i will tell you this, w/the weight gain of that much in short time and hyporeflex in lower extremity points to hypothyroid. This is what i am dealing w/myself, did not need a cane to ambulate until the weight came upon me. 10#'s, next mth 12#'s by the time i got the doc's to do a third generation TSH test i had packed on 52#'s. Now i cannot walk very far w/o cane and back brace. Get your TSH checked ASAP. Are you losing hair? Are you cold more often? Constipated more than usual? Fingernails growing out "flat" then have like a "beak" when they get a little longer? All of these are signs of hypothyroid. My TSH was "normal", i said no it's not, got the third generation TSH "Oh you are hypothyroid" duh, too late 50+ lbs later. Good luck, get checked, don't wait till it's too late.