Weight gain question

I keep seeing posts where people are 20wks and glad they have only gained 0-3lbs or have even lost weight!  Even if you are obese your supposed to gain 11-20lbs during pregnancy!  Are people's doctors recommending they try to gain nothing or lose weight during their pregnancy? My doctor told me by 20weeks I should have gained between 5-7lbs.  I was definitely overweight when I started (sadly).  What have your doctors said about your minimal or negative gains?