17 days post Smart Lipo on arms. Do I have swelling above elbow or is it still fat?

Arms can develop a large degree of swelling if compression garments are not properly worn or not tight enough. Double check with your surgeon to see if you have a hematoma. If they were smaller after lipo, it's probably fluid. Fat doesn't magically grow back. Go for massages as well.

After a Smart Lipo procedure, it’s common
for swelling to last for several weeks to a few months. What you’re
experiencing should dissipate over time, and the best thing you can do to aid
in the healing process is to continue wearing your compression garment as
directed by your surgeon, as well as keeping your sodium intake low. It’s
common for swelling to occur in the lowest part of the treated area, which for
you lands at the elbows. This may explain the current size and tenderness of
that location. If you continue to be concerned or uncomfortable, it’s important
that you follow up with your surgeon.

Despite not having photos, what you are describing is very common when it comes to SmartLipo of the arms. At first, you noticed that the arms were smaller, including the area above the elbow. After two weeks, swelling or edema of the skin and soft tissues settled to the lowest part of the treated area which lies just above the elbows. This is because gravity will tend to draw the swelling to the most dependent portion of the operated areas. Luckily, the fat that has been removed with the operation is gone permanently and the swelling that is temporarily taking up the space above the elbow will dissipate in a few weeks to months to allow the slimming result to show. Wearing the compression garment is helpful; just make sure it starts at the wrist because it will cause swelling just beyond the cuff. 

Thank you for your question. It is common to have swelling after liposuction. It is very early to comment whether it is swelling or Fat. Swelling will continue to go down next few weeks. After few weeks it will be better reevaluate to see if it is fat or not. We recommend in general 6 months to wait if we need to do any revision. If it is a fat it can be easily fixed. Good Luck

Thank you for your question. Without before and after photos
it is hard to determine what the situation may be. However, swelling post
SmartLipo is a completely normal part of the healing process. For the next 6-8
weeks the swelling will come and go, this is your body’s way of healing. Make
sure to continue wearing your compression garment and follow up with your
surgeon.

It's too soon to tell since it's only been two weeks and two days since your Smart Lipo procedure.It is most likely swelling due to all the tumescent fluid that was injected into your arms. You mention that "it looked to be gone at 1st site" and that is probably because the fat was gone, but then the swelling came.Wait another month and this will clarify itself.Cheers

Without seeing pre and post-op results, it is difficult to say what might be going on.  What you are describing may be related to swelling.