Pretty much as it says on the tin: fat injections are injections of fat – your own fat. The fat is used as a filler to plump up areas of the face that need a boost, such as the area around the eyes, which can become hollow-looking as you age.

You’ll also see this type of treatment described as ‘lipomodelling’ or (in good old Anglo-Saxon) as ‘fat graft’, or sometimes ‘microfat’ or ‘nanofat’ injections.

Fat injections are considered safe but you will need to find an expert practitioner to give the results you’re looking for. Unlike most types of filler, fat is entirely natural – and it’s your fat, so it’s fully compatible with your body.

Liposuction, on the other hand, is considered to carry major risks. As you know, liposuction is invasive surgery: it involves an incision to the body and the use of surgical equipment inside the body, to extract the fat. However, most practitioners extracting fat for injecting into the face will be able to gather enough fat using a slim cannula that is slipped through a small hole in the skin that can be closed with a steri-strip (i.e. it is small enough not to need stitching).

Yes, fat injections are an effective treatment for adding a modest amount of volume to the face. Injecting fat adds volume not only through the bulk of the fat but also its properties for promoting healing. The uncertainty about the result of fat injections is that while many of them will take root in their new location, some won’t, and will die off before they have established themselves.

Your fat contains what are called ‘mesenchymal cells’, cells that contain stem cells that can develop into whatever sort of tissue is needed. You may see these cells described as ‘adipose-derived mesenchymal cells’ because they’re derived from adipose (fatty) tissue. When these cells are injected into the face, they not only help plump it up from the inside out but also promote healing from deep within the facial tissues.

First, the practitioner uses liposuction to extract fat from an area of the body where you have a surplus, such as your stomach or your thighs, under local anaesthetic. Only a small amount of fat is needed – for example, one to two teaspoons’ worth is needed to restore a youthful look to hollowing eyes – so there isn’t a big difference at the extraction site.

The practitioner then emulsifies the fat by forcing it repeatedly through a fine filter until it is in a fluid state suitable for injecting. After that, the practitioner injects the fat into the treatment area.

You’ll certainly feel the injections, but most people don’t find them painful. The practitioner may numb the whole treatment area with anaesthetic cream beforehand, of if they are planning to work deeply, they may sedate you, to keep you still as well as comfortable.

The fat harvesting via liposuction does require local anaesthesia.

You can use the Find a Practitioner tool on this website to find a practitioner who offers fat injections.

Fat injections vary greatly in cost depending on which area you’re having treated. Here are two examples to give you a rough idea:

• Fat injections around the eyes: from £2,500
• Full-face makeover using fat injections: from £10,000

The entire procedure, from harvesting the fat to injecting it, usually takes an hour or two.

The effects of fat injections last for around five years.

Yes, there are side effects to fat injections. The following list shows side effects you should expect:

• Bruising and swelling. Both the extraction site and the injection sites are likely to bruise and swell.
• Numbness. You may experience temporary numbness at both the extraction site and the injection sites.
• Fat loss. Some of the injected fat is likely to be lost over several months; about 25% is typical. The practitioner could pre-empt this problem by injecting more fat than is actually needed, but then you’ll have an overfilled ‘pillow face’ until the extra fat is lost.
• Scarring. You may have minor scars at the extraction site.

You will need to keep your weight stable after the treatment, too. When you eat more than you need to, the excess will be stored as fat, which means that the existing fat cells in your body will expand. The fat cells around your waist will expand, the fat cells around your backside will expand… and so will the newly transplanted fat cells in your face.

If things go wrong – which they shouldn’t – the following side effects can occur:

• Fat necrosis. This is when fat tissue dies off because of injury. Scar tissue then forms.
• Haematoma. This is when a pool of blood forms below the skin.
• Fat embolism. A loose piece of fat can cause a blockage in a blood vessel.

Your experience of having fat injections will vary considerably depending on which area you’re having treated.

Because getting the fat for the injections requires you to have liposuction, having fat injections is a serious treatment that you should research in depth and discuss in detail with the practitioner. The practitioner will be able to tell you what to expect during the treatment you have chosen.

In particular, make sure you know how much ‘downtime’ you will need to recover from the liposuction and the injections. For example, you may need to take time off work while you recover from the liposuction, and while the swelling in your face reduces.