Can Healthy Weight Loss Reduce a Lipoma?

I would agree with the previous answer that fat cells in a lipoma are under different controls than normal fat cells and will not specifically respond to weight loss that shrinks other fat cells in the body.
Lipomas are a benign tumor of fat cells. They only cause problems because of their size and location but can be unsightly. Fortunately, in many cases, it is possible to treat them the same way liposuction treats other areas of unwanted fat cells. If you inherit an excess number of fat cells in certain areas they will increase or decrease in size with your weight but they won't go away. The number of fat cells and your proportion remains the same.
Liposuction removes them permanently with a minimum of scar and potential damage. For lipomas to be treated with liposuction, they must usually be below the skin (subcutaneous) rather than deeper or they need to be verified as lipomas (biopsy) and not some other type of tumor. Liposuction may not remove the entire lipoma, which is not a problem if the contour issue is resolved but would be a problem if the lipoma was actually a more serious type of tumor and residual tumor would lead to recurrence.
For small to medium size subcutaneous lipomas (not the large one in the picture), an extraction technique can be done that involves a liposuction-size incision and instrument/manual extraction rather than suction. For the lipoma in the picture, assuming it is a lipoma, I would recommend liposuction reduction/removal.

The cells that constitute a lipoma seem to be under a different control system than ordinary fat system. Weight loss does not seem to have much of an effect. There are reports of people who lost massive amounts of weight, starvation (diet or otherwise) losing some mass in a lipoma but for practical purposes weight loss will not have an influence.