The process of reducing localized fat deposits with injectable treatments is not instantaneous, relying on a biological mechanism that requires time to complete. These injections commonly utilize a synthetic form of deoxycholic acid, designed to treat specific, stubborn areas of fat. Deoxycholic acid is a naturally occurring molecule that helps the body break down and absorb dietary fat. The U.S. Food and Drug Administration (FDA) has approved this treatment for improving the appearance of moderate to severe fat below the chin (submental fat). Understanding the body’s response is crucial, as the timeline for visible change is tied directly to cellular destruction and natural waste elimination.
How Fat Dissolving Injections Work
The mechanism of action centers on cytolysis, or cell destruction. Once the deoxycholic acid solution is injected into the targeted subcutaneous fat, it acts as a cytolytic agent. It physically destroys the membranes of the fat cells (adipocytes). The compound emulsifies the fat, causing the cell to rupture and breaking down the fat cell wall.
Following cell destruction, an inflammatory tissue reaction begins. The immune system recognizes these ruptured cells and their contents as waste material to be processed. Macrophages move into the area to clear away the debris, relying on the lymphatic system and metabolic pathways. This biological clean-up and elimination phase dictates the overall timeline for visible results, making the change gradual rather than immediate.
Immediate Post-Treatment Swelling and Recovery
The body’s immediate inflammatory reaction is a significant factor in the initial post-treatment appearance. Directly following the injection, the treated area will experience swelling, bruising, and often tenderness or pain. This swelling is an expected part of the healing process, signaling that the deoxycholic acid is actively destroying fat cells. Acute swelling can sometimes make the treated area temporarily appear fuller than it did before the procedure.
This initial fullness is transient and is not a sign of treatment failure; rather, it indicates the biological process is underway. Swelling typically peaks within the first 24 to 48 hours after the session. For most patients, this acute swelling and associated tenderness begin to subside significantly over the next two to four weeks. Other common side effects, such as numbness, redness, or firmness, may also be present as the tissue heals. The resolution of these immediate side effects is the first step toward seeing the actual fat reduction.
The Timeline for Achieving Final Results
Visible fat reduction is not apparent until the majority of the post-injection swelling has resolved. The first signs of a noticeable change typically begin to emerge approximately four to six weeks following a single treatment session. This period allows sufficient time for the body to metabolize and eliminate a substantial portion of the destroyed fat cells.
The majority of patients require a series of treatments to achieve their desired contouring goal. A treatment plan commonly includes two to four sessions, though up to six may be necessary depending on the volume of fat addressed. Sessions are spaced at least one month apart to give the body adequate time to process the destroyed fat cells and allow previous swelling to diminish.
Several factors influence the overall timeline, including the individual’s metabolic rate and the amount of fat in the treated area. A faster metabolism can sometimes accelerate the rate at which the body eliminates the waste product. Final, optimal results are generally observed one to two months after the last required injection session. Since the injected substance permanently destroys the fat cells, the results are considered long-lasting, provided a stable weight is maintained.