It is hard to say without seeing the size of the character, what sort of settings you are using for the proxy mesh or what kinda animation you are trying to do. There are a few things you could try.
First thing I would look at is the pin group for the proxy mesh. You could add some weight painting to help support the arms so they don’t sag. Try a low strength brush and add weight to the pin group to the parts that don’t need to jiggle as much. Parts near the wrist, elbow and shoulder which tend to be where the fat isn’t as thick could be weight painted more heavily
You could try increasing the shinking factor under the shape section in the cloth physics, though it make the arm less jiggly.
But without seeing a picture, it is a bit difficult to say anything concrete