Ablative lasers and cellulite
There are two types of therapeutic lasers, ablative lasers (also known as "hot" lasers, or high energy lasers), and non-ablative lasers (also known as "cold" lasers, or low level lasers).
Ablative lasers are used for acne, tattoo removal, skin resurfacing, hair removal and for surgery (e.g. for cutting skin or other tissue). High energy lasers are able to ablate (i.e. to excise, amputate, remove by erosion/melting/evaporation or otherwise destroy body tissue). In that sense, we can say that high energy levels work through "brute force".
Ablative lasers are really good at treating superficial tissues by creating controlled damage, as in removing part of - or break down components of - the upper surface of the skin (epidermis) in order to remove acne, tattoos, wrinkles and other blemishes. However, cellulite is found in the deepest layer of the skin and thereby it simply cannot be removed by hot lasers without first burning away (ablating) the rest of the skin itself (which is, obviously, not an option).
So all those IPL machines and hair removal lasers cannot be used to remove cellulite too - despite the marketing hype.
Surgical lasers, fat removal and cellulite
Having said all that, there is a case where ablative lasers are successfully used to melt fat (but NOT cellulite): that of laser-assisted liposuction, also known as smart-lipo, mini-lipo or laser liposuction (the latter should not be confused with the gimmicky, non-surgical "laser lipo", analysed below). For smartlipo, a cannula is inserted underneath the skin (and therefore UNDER the cellulite layer) and melts the deep subcutaneous fat, which is then aspirated (sucked) out of the body more easily.
Smart lipo, or mini lipo, is great for removal of limited amounts of fat (normal lipo is better for larger amounts of fat), but it is an invasive liposuction procedure which usually causes quite a lot of scar tissue / skin hardening / fibrosis, and in addition it does NOT remove cellulite (cellulite is an integral part of the skin and therefore can not be removed).
Cellulaze is an implementation of a hot/ablative laser, such as the one used for laser liposuction, but for cellulite. Whilst laser liposuction targets the fat under the cellulite layer with a laser-tipped cannula, cellulaze targets the cellulite layer itself, also with a laser-tipped cannula.
For cellulaze the cannula is inserted into the skin, under the cellulite layer, and fires upwards onto the cellulite layer, aiming to basically cauterise/burn it. In theory this causes thermal (heat) damage of the cellulite fat and tightens the skin by burning / coagulating it.
As always, in practice things are not as good as on paper, because the power needed to burn the fat above the cannula, is so strong that it does not cause simple coagulation, it very often causes severe scarring which manifests as hardened skin bumps.
So the end result is that you replace the cellulite bumps with scar tissue bumps. I have personally seen some quite bad hardened scar bumps on clients who had cellulaze, which where much bigger /worse than the cellulite they had before, with the cellulite around them not affected in the slightest. If I was a woman with cellulite, the last thing I would do is shell out £3000-£5000 for that result...
No wonder then that cellulaze did not really catch on in the UK, despite the huge initial hype.
We saw above that cellulaze quite often replaces the cellulite bumps with scar tissue bumps, sometimes worse than the original ones. Instead of scars though, cellfina, the latest cellulite laser minimally invasive surgery, replaces the cellulite appearance with flabbiness.
With cellfina, a tiny laser tipped cannula is inserted next to a cellulite indentation, side-fires the laser on it and cuts the shortened, hardened connective tissue fibres that anchor the indented skin to the tissue underneath. This sets free the anchored skin of that specific indentation and restores the smooth appearance of the skin on that specific spot. Then another spot is chosen, another anchor is released and so on...
This sounds great on paper, but not so much in practice. Let me explain. Have you ever wondered why mother nature created those collagen "tethers" that keep your skin attached to your deeper tissues? Exactly: those collagen tethers exist to ensure skin stays put and doesn't glide sideways, like a wobbly fruit jelly.
By undercutting what keeps skin in place, you replace one evil with another: you replace cellulite with wobbly, flabby, loose, saggy skin. Given that most women with cellulite already have loose, saggy skin, I don't know what is worse: cellulite with some wobbly skin, or no cellulite with VERY wobbly skin on that spot.
Which takes us to the next point. There is a reason why I typed "one that spot" with italics: with cellfina you can only "release" the cellulite anchoring fibres one at a time. Given that the female legs have hundreds of those anchors, it is obvious that not all will be treated - not in one surgery session, anyway.
And if all of them are treated, then you will be left with no septae, as they are called, i.e. no tethers, no anchoring points to keep your skin in place. Of course some anchoring will still remain where skin and deep fascia fuse into each other, or where the anchoring points are not shortened enough to create the cellulite effect on that spot. But get ready to wobble A LOT. So...
...after cellfina a course of strong radiofrequency treatments is a must in order to treat the newly acquired skin looseness.
But then again, a course of strong radiofrequency treatments without cellfina would have improved the cellulite anyway, and would have actually boosted firmness, instead of - literally - undermining it, so why have cellfina in the first place?
And there is one more thing: cellfina realistically only works on a few dozens of the hundreds of large, deep hypodermal anchors, the ones that cause the deep cellulite indentations. That is what cellulite experts call "deep cellulite".
However, cellulite also comprises literally thousands of smaller, superficial dermal/hypodermal anchors, i.e. "superficial cellulite". For those thousands of small but annoying cellulite bumps, cellfina can do nothing, as those bumps are part of the dermis itself, not part of the hypodermis where cellfina works, so these thousands of smaller bumps will continue to exist after cellfina surgery.
All in all, this laser cellulite procedure is destined for the really desperate with really, really bad cellulite indentations. In that case, cellfina will make those deep, bad cellulite indentations disappear, and in that case perhaps the resulting skin wobbliness is better than the cellulite bumps. As long as you don't move or shake your booty too much though...
"Laser lipo", fat melting and cellulite
In contrast to ablative lasers, low level laser therapy (LLLT) or cold laser therapy is very gentle and is used in physiotherapy as a therapeutic stimulus for superficial tissues, such as superficial tendons and ligaments. We could say that cold lasers work by "gentle stimulation", as opposed to the brute force of high energy ablative lasers.
Similarly to ablative lasers, the problem with cold lasers is that they do not penetrate enough to reach the subdermis, i.e. the innermost layer of the skin, where cellulite is located.
Moreover, the power used for low level laser therapy is tiny and definitely not enough to justify the claims of fat melting and other lies propagated by cold laser cellulite treatment providers. Most LLLT, so called "laser lipo" machines have a total power of around 200mW to 2W, which pales in comparison with the good monopolar radiofrequency or ultrasound cavitation machines that feature powers of as much as 200W, i.e. one 100x to 1000x times more power!
Given that with the strongest cavitation/radiofrequency machines, a course of 6~12 sessions is recommended for satisfactory results for cellulite reduction, one can imagine what a machine with 1,000 times less power can achieve: nothing. Clearly "fat melting", "non-surgical fat removal" and "getting rid of your cellulite" are not one of those results.
Low level laser non-surgical "fat removal" treatments are so "effective" that they sell for as low as £10-20 per session on Groupon and similar websites - and of course no one is getting slimmer...
Although LLLT has a place in physiotherapy, all that cold laser fat removal treatments will remove is your money, so don't fall prey to unscrupulous cellulite / "fat removal" treatment providers.
LED therapy is not laser therapy and it is equally ineffective for cellulite
Quite a few "cellulite removal" machines, that according to their marketing are supposed to use laser, in fact use light emitting diodes (LEDs). LEDs are different from lasers, in that the light beam that they produce is not as concentrated and coherent as in cold lasers. However, LEDs are similar to lasers in that they are equally ineffective in treating cellulite, given their low power (also 200mW to 2W).
Most anti-cellulite machines that feature LEDs (and advertised as lasers) are combination LED+suction massage_bipolar radiofrequency machines. The problem with such machines (in addition to the fact that LEDs do not reduce cellulite), is that their bipolar radiofrequency currents are of too low a power (typically 50W), and of too superficial a penetration (1-5mm) to produce satisfactory results for cellulite reduction. To make matters worse, the suction used for those treatments tends to cause spider veins (thread veins) and skin looseness, actually making matters worse.
All in all, lasers do not "really work" for cellulite
In summary none of the options above are ideal for cellulite, with only cellfina being relatively effective, replacing however cellulite with skin sagginess. It's all relative, I suppose, and with cellfina, followed by lots of strong radiofrequency treatments afterwards, things can look somewhat better.