A “double chin” is not a single diagnosis. The visible fullness under the chin can come from submental fat, loose neck skin, weak platysma muscle tone, low-positioned salivary glands, a short chin, or a combination of all of these. Liposuction treats the fat layer. It does not move a low hyoid bone, shrink a prominent submandibular gland, or tighten a neck that has heavy vertical bands.
The most liposuction-friendly presentation is a soft, pinchable pad of fat between the chin crease and the upper neck, with skin that springs back when it is lifted and released. That patient may have a full profile in side-view photographs despite a stable weight and otherwise balanced face. Removing the fat lets the skin redrape closer to the jawline and improves the angle between the chin and neck.
A different patient has little fat but a loose sheet of skin hanging below the jaw. Another has two vertical platysma bands visible when speaking or clenching. Another has fullness sitting deeper and lower, where glandular ptosis rather than fat is the main issue. These patients may still improve with a combined plan, but liposuction alone would under-deliver. The consultation therefore starts by separating fat from skin, muscle, and glandular causes before any price or technique is promised.