I have had the same issue with gaining weight! I don't eat a lot and when I do, I eat a fairly organic/ healthy diet so I know it's not what I eat. We are taking steroids so it is difficult to maintain/ control our weight.

Before I knew I had kidney issues I was easily about 80 pounds of water. It was literally leaking through my legs. You should ask to be referred to a nephrologist.(Kidney Doctor) Better to be safe than sorry.

I have had weight issues with my lupus but with my thyroid, has anyone checked your thyroid which is also an autoimmune issue.

Hey. Sorry to hear about your unpleasant visit with your rheumatologist. I as well had the same experience. Good thing you changed doctors. Your biggest advocate is yourself.
But to answer our question. Yes lupus can affect your weight. For example I gained about 60 pounds. I got so big my family thought I was pregnant. But turns our it was all water weight because lupus was causing problems with my kidneys which made me retain 60 pounds of water. I even started to literally leak water though my skin. & still my rheumatologist thought nothing was wrong..
Also Prednisone can make you gain weight. & since your new to lupus in case you don't know prednisone are steroids.
However In November I was released from the hospital after a to month stay I had lost all the water weight. I lost about 80 pounds. But since then I have gained back about 30 pounds.

Since your fairly new to the diagnoses I have a blog if you are interested in reading my story and journey from the beginning to now...

sarasmiles26.blogspot.com

An emergency room doctor asked me if he could test me for lupus so I said okay and when the results came back positive and I showed them to my general practitioner he said he didn't believe it so I decided to find a good rheumatologist and he takes very good care of me. You have to keep asking questions and if you don't think they are listening go somewhere else.