Fat grafting — not all of it survives, and how much will cannot be known in advance

Sometimes a face looks older because it has hollowed, not descended — under the cheekbone, at the temple, under the eye, across the forehead. Lifting such a face can make it look gaunter.

Fat grafting fills those spaces with your own fat. There are three steps: harvest from thigh or abdomen, purify (by centrifuge or similar), and place it in small portions through a fine cannula.

It gets compared with filler, but it behaves differently. Filler is broken down slowly and eventually goes, and it can be dissolved. Grafted fat, if it survives, stays — it is your own tissue.

That is also where the difficulty lies. Not all of what goes in survives. Fat cells that do not get a blood supply are resorbed, and how much remains varies by area, technique and person. So it is often done in stages, or over-filled to allow for what will be lost.

The gravest risk, though very rare, is fat entering a blood vessel. If it blocks a vessel supplying the eye or brain, blindness or stroke can follow. It is extremely uncommon and cannot be undone — the same class of risk as filler injection. Areas laced with vessels, such as the glabella, nose and forehead, demand particular care.

The take rate is unpredictable. Even the two sides of the same face can hold differently. Judge the result at three to six months.

Lumps and nodules can be felt. Too much placed in one spot leaves the centre without blood supply, and it can harden or calcify.

Where the fat was taken from is also an operated site. Bruising and soreness at the thigh or abdomen, and rarely contour irregularity.

Over-correction is a common way for this to go wrong. Place extra expecting resorption, and if more survives than expected, a swollen look becomes the fixed result.

If vision blurs suddenly, if pain becomes severe, or if the skin goes pale, report it immediately.

Do it at a stable weight. Grafted fat is your fat, so it grows when you gain and shrinks when you lose. If you are in the middle of losing weight, afterwards is better.

Do not plan on one session. Splitting it over two often gives a more even result than putting it all in at once.

Not smoking matters. Whether grafted fat survives depends on new vessels growing into it, and smoking interferes with that directly.

Settle first whether the problem is descent or hollowing. If descent dominates, filling alone can look heavy. Read alongside facelift.

Do not press or massage the grafted area for the first few weeks. It is settling.

How much can be undone sits awkwardly in the middle. Some is resorbed, so it is not fully permanent; but what survives is your own tissue and cannot be dissolved the way filler can. Putting in too much means an operation to take it out, and that is not easy.

Whether filler or fat suits you is decided by volume and duration. For a small trial amount, filler is better — it can be dissolved if you dislike it. For a wide area you want to keep, this is the option.

Results vary widely. Take rates are said to differ with who performs it, and a reader has no way to know that difference in advance.

Whether to have it done is settled with a doctor, and it is better not to settle it on one consultation alone.