The size and location of the lipoma will ultimately determine how quickly you can return to exercise. In general, though, my patients rarely have any down time, even with lipomas the size of my fist.
While lipoma fat is indistinguishable by look, or even under the microscope, from normal fat--- the lipoma tends to readily separate from the surrounding tissue with minimal dissection. Because of this, the actual surgical scar is often only a fraction of the size of the lipoma. Of the hundreds of lipomas I have removed, the surgical incision is rarely more than 1-inch. Further, virtually all lipomas can be removed as an in office procedure with only local anesthesia.
I tell my patients to take it easy for the next 24 hours, then let their bodies be their guide. If exercise becomes painful, your pushing to hard. Ultimately, though, even if you push to hard, the primary risk is suture breakage and a larger scar.
Most patients can return to limited exercise in 24 hours, and full exercise in a few days-- of course, depending on the size and location of the lesion removed.