Hi Wendy,
There are many proposed solutions for lipomas, although I've never seen any work. It would be great if someone on the list has different experience and weighs in on your question. Most herbal approaches center around draining Damp and tonifying Yang, so if a Damp or Yang tonic formula seems appropriate, you could always give that a try. I do find that, at least on the diet you're using, lipoma growth tends to be more limited. They never seem to become huge, in the dogs I've seen.
Lately I'm trying homeopathic Thuja for lipomas. No outcomes yet to report, but it is one of the few homeopathics with that indication.
Sorry I'm not much more help to you than this.
Steve