Short answer
Mainly because of fat embolism: fat injected into the buttocks can reach the bloodstream and block the blood vessels of the lungs, which can be fatal. In 2018, international plastic surgery societies estimated the death rate at up to 1 in 3,000 procedures, higher than any other cosmetic operation at the time. Changes in technique, especially avoiding injection deep into the muscle, appear to have reduced the risk, but it has not been removed, and safety depends heavily on how and by whom the operation is done.
Key points
- A Brazilian butt lift (BBL) is liposuction plus injection of the removed fat into the buttocks.
- The main cause of death is pulmonary fat embolism (fat blocking blood flow in the lungs).
- Deaths were linked to fat placed deep in the buttock muscle; guidance now advises against deep muscle injection.
- A 2020 survey suggested fat embolism became less common after the guidance, but the figures are self-reported.
- Other risks include blood clots, infection, fluid collections and fat necrosis (death of the grafted fat).
What a BBL involves
Despite the name, a BBL is not a lift. It is gluteal fat grafting: fat is removed by liposuction from areas such as the abdomen or flanks, processed, and then injected in small amounts across the buttocks.56 It is done under sedation or general anaesthesia.6
That makes it two operations in one. The surgeon may remove up to three times more fat than is injected, and on average about 60–80% of the transferred fat survives.6 Each part carries its own risks.
Why it is considered high risk
The defining danger is pulmonary fat embolism. In 2017, a task force from the Aesthetic Surgery Education and Research Foundation (ASERF) studied deaths after gluteal fat grafting using a surgeon survey, interviews, autopsy reports and coroner records.1 It identified large-volume fat embolism to the lungs, causing sudden collapse of heart and lung function, as the cause of death.1
The task force linked these deaths to fat being injected deep into the buttock muscle, and reported lower, though not zero, risk with injection into more superficial layers.1 It recommended avoiding deep muscle injection, using wider single-hole cannulas of at least 4.1 mm and avoiding angling the cannula downwards.1
In 2018, the American Society of Plastic Surgeons (ASPS), the American Society for Aesthetic Plastic Surgery and the International Society of Aesthetic Plastic Surgery issued a joint warning that the mortality rate might be as high as 1 in 3,000, far higher than any other cosmetic surgery.3 They pointed to the technical difficulty of the operation and the growing number of surgeons without plastic surgery training performing it.3
How certain are the numbers?
Not very. The 2017 estimates ranged from about 1 in 6,214 to 1 in 2,351 depending on the method, and the authors said none should be treated as the true rate, which was likely higher.1 The incidence of death is best described as Uncertain incidence.
A follow-up survey published in 2020 found that reported deep muscle injection fell from 13.1% to 0.8% of surgeons after the recommendations.2 Reported fat embolism fell from 1 in 1,030 to 1 in 2,492 procedures, and mortality showed a downward trend.2 These are self-reported survey figures from society members, so they may not reflect practice more widely.
| Report | What it found | Main limitation |
|---|---|---|
| ASERF task force, 2017 | Deaths from fat embolism; estimates 1 in 6,214 to 1 in 2,3511 | 14% survey response; true rate likely higher |
| Multi-society warning, 2018 | Mortality possibly up to 1 in 3,0003 | Based on the same limited data |
| Follow-up survey, 2020 | Less deep injection; fat embolism less often reported2 | Self-reported; members of societies only |
Other risks
Beyond fat embolism, ASPS lists deep vein thrombosis (a blood clot in a deep vein), heart and lung complications, anaesthesia reactions, bleeding, seroma (fluid build-up), infection, poor wound healing, asymmetry, numbness, prolonged swelling, fat necrosis and the possible need for revision surgery.4
Results can also change. Some grafted fat is absorbed, and the transferred fat grows or shrinks with body weight like other fat.6
What affects safety
- The depth of injection: avoiding deep muscle injection is the central recommendation.1
- Cannula size, design and angle.1
- The surgeon’s training; the societies warned about operations by surgeons outside plastic surgery.3
When to seek medical advice
Call 999 or go to A&E if you develop shortness of breath or chest pain after surgery, especially with pain or swelling in one leg; a blood clot that reaches the lungs can be life-threatening.7 Contact the surgical team promptly about increasing pain, swelling or signs of wound infection.
Common questions
Is a BBL still dangerous today?
The risk appears lower than in 2017 where surgeons follow the newer recommendations, but it has not disappeared.2 Even superficial injection carried some risk in the task force data.1
What does “subcutaneous only” mean?
It means placing fat in the layer beneath the skin and above the muscle, rather than into the muscle. This reflects the recommendation to avoid deep muscle injection.1
Will all the fat stay?
No; on average about 60–80% of transferred fat is retained, and final results take around a year to judge.6
Bottom line
The BBL earned its reputation because fat injected deep into the buttock muscle caused deaths from fat embolism at a rate unmatched by other cosmetic operations. Safer technique appears to have reduced that risk, but the exact rate remains uncertain, and the surgeon’s method and training matter greatly.
Related reading
- Plastic surgery overview
- Risks of multiple procedures in one operation
- Blood clot risk when flying after surgery
- Who performs my surgery?
- Medical travel red flags
Sources
- Mofid MM, Teitelbaum S, Suissa D, Ramirez-Montañana A, Astarita DC, Mendieta C, Singer R. Report on mortality from gluteal fat grafting: recommendations from the ASERF Task Force. Aesthetic Surgery Journal; 2017;37(7):796-806. doi:10.1093/asj/sjx004. https://doi.org/10.1093/asj/sjx004
- Rios L Jr, Gupta V. Improvement in Brazilian butt lift (BBL) safety with the current recommendations from ASERF, ASAPS, and ISAPS. Aesthetic Surgery Journal; 2020;40(8):864-870. doi:10.1093/asj/sjaa098. https://doi.org/10.1093/asj/sjaa098
- American Society of Plastic Surgeons. Plastic surgery societies issue urgent warning about the risks associated with Brazilian butt lifts. ASPS press release; 2018. https://www.plasticsurgery.org/news/press-releases/plastic-surgery-societies-issue-urgent-warning-about-the-risks-associated-with-brazilian-butt-lifts. Accessed 5 November 2026.
- American Society of Plastic Surgeons. Buttock enhancement: risks and safety. ASPS. https://www.plasticsurgery.org/cosmetic-procedures/buttock-enhancement/safety. Accessed 5 November 2026.
- American Society of Plastic Surgeons. Buttock enhancement. ASPS. https://www.plasticsurgery.org/cosmetic-procedures/buttock-enhancement. Accessed 5 November 2026.
- American Society of Plastic Surgeons. Buttock enhancement procedure steps. ASPS. https://www.plasticsurgery.org/cosmetic-procedures/buttock-enhancement/procedure. Accessed 5 November 2026.
- NHS. Deep vein thrombosis (DVT). NHS website. https://www.nhs.uk/conditions/deep-vein-thrombosis-dvt/. Accessed 5 November 2026.
Article history
- — First published.