In this guide15 sections
- Key Points
- What Does a Flat Bum Look Like?
- Why Is My Bum Flat?
- Does Your Bum Get Flatter With Age?
- Flat Bum vs Saggy Bum: What’s the Difference?
- What Is Flat Butt Syndrome (Dead Butt Syndrome)?
- Flat Bum Exercises: Can You Fix a Flat Bum With Exercise?
- How Long Does It Take to Fix a Flat Bum?
- How to Fix a Flat Bum Without Surgery
- Flat Bum Surgery: BBL, Implants or Buttock Lift?
- What If You’re Too Slim for a BBL?
- Flat Bum Before and After
- Frequently Asked Questions
- Flat Bum Surgery in London
- References
Key Points
- A flat bum comes down to four things: frame, fat, muscle and skin. Your pelvis sets the outline, fat and muscle give projection, and skin decides whether the buttock sits high or drops.
- Exercise fixes only the muscle part. In a 9-week MRI trial, hip thrusts and squats grew the glutes by similar amounts, but training cannot add fat or change your bones.
- Bums do get flatter with age and weight loss. Buttock volume falls and the crease lengthens with age, more so in women, and weight loss shrinks buttock fat.
- Dead butt syndrome is not the same as a flat bum. It is an informal name for under-active glutes, often linked with long hours of sitting, and it is a job for a physiotherapist.
- Fat transfer has the lowest complication rate of the surgical options. A review of 4,362 patients found complications in 6.8% after fat grafting, 23.1% after flap techniques and 31.4% after implants.
- The right fix depends on what is missing. A BBL suits a BMI of about 23 to 28, a skinny BBL a BMI below 23, implants suit people with very little spare fat, and a buttock lift treats loose skin.
A flat bum is usually caused by a combination of your bone structure, how much fat your body stores on the buttocks, the size of your gluteal muscles and the quality of your skin. Exercise can build the muscle and lift the shape a little, but it cannot add fat or change your pelvis, so a genuinely flat bum often needs added volume from fat transfer with a Brazilian butt lift (BBL), buttock implants or, where loose skin is the main problem, a buttock lift.
This guide explains what a flat bum (also called a flat butt, flat buttocks or a “pancake bum” or “pancake butt”) looks like, why your bum has gone flat, whether it gets flatter with age or after pregnancy, what flat butt syndrome is, how far flat bum exercises can take you, and how to get rid of a flat bum with treatment, from a liquid BBL to flat bum surgery. If your main worry is drooping rather than flatness, see our guide on how to get rid of saggy buttocks.
What Does a Flat Bum Look Like?
A flat bum is a buttock with little projection. Seen from the side, the curve from the lower back to the top of the thigh is shallow rather than rounded. Typical signs include:
- Little projection in profile. The fullest point of the buttock sits barely behind the line of the back and thighs.
- A square or “pancake” outline from behind, wide and short rather than round.
- A faint lower crease, with the buttock blending straight into the thigh.
- Hollow outer sides. Hip dips, an inward curve below the hip bone, make the bum look flatter from behind.
- Trousers and dresses that sag at the seat even when they fit at the waist.
A flat bottom is common and is not a medical problem. If it bothers you, the useful question is which part of the buttock is responsible.
Why Is My Bum Flat?
Plastic surgeons assess the buttock by its bony frame, the gluteal muscles, the fat over them and the skin on top. The 2018 gluteal classification system revisited in Clinics in Plastic Surgery ↗ uses these building blocks, along with pelvic shape and fat distribution, to plan buttock reshaping[1]. Each one can make a bum look flat:
- Frame. A narrow or straight pelvis gives a squarer, flatter look, and a flatter lower back reduces how far the bum appears to stick out. Only added volume over the top changes this.
- Fat. Much of the roundness of the buttock is fat. Some people store fat on the tummy and flanks rather than the buttocks, and a slim build or weight loss leaves little volume to shape.
- Muscle. Small or under-used glutes give less lift and projection, particularly at the top of the buttock.
- Skin. Loose or thin skin lets the buttock drop and spread, flattening the upper half.
Most people have a mix. Your buttock type matters too, as square, round, A-shaped and V-shaped buttocks flatten in different places. Our guide to BBL shapes and butt types explains how surgeons use them to plan a result.
Why has my bum gone flat after weight loss?
A flat bum after weight loss is common. Losing weight takes fat from everywhere, including the buttocks. Fast weight loss, including on GLP-1 weight-loss injections, can also take some muscle and leave skin that cannot shrink back, so the buttock flattens and drops at once. Our article on Ozempic butt explains why it happens, how strength training and protein protect the muscle while you lose weight, and when surgery helps. Your weight should be stable for at least 3 months, and 6 to 12 months after major weight loss, before surgery.
Why is my bum flat after pregnancy?
A flat bum after pregnancy is common. Weight change, less exercise in the months after the birth and breastfeeding can all reduce buttock fat and glute strength, and carrying a baby changes posture for a while. Glute training usually helps once you are cleared to exercise. If the shape has not come back once your weight has been stable for at least 3 months and you have stopped breastfeeding, a BBL can restore volume; our guide to BBL and pregnancy explains the timing.
Does Your Bum Get Flatter With Age?
Yes. The buttock gradually loses volume and drops with age, and the change is more marked in women. In a study of 280 volunteers aged 15 to 85, women showed more muscle and volume loss and more drooping of the buttock with age than men[2]. Typical changes are less volume in the upper buttock, a longer and deeper crease underneath, and thinner, less elastic skin. Menopause can speed this up, as falling oestrogen shifts fat storage towards the tummy. Strength training slows muscle loss at any age, but it does not restore lost fat or tighten skin.
Flat Bum vs Saggy Bum: What’s the Difference?
The two often appear together, but they need different fixes:
- A flat bum lacks volume. The skin may be firm and the crease in a normal place. The fix is to add volume with fat, an implant or, to a lesser degree, muscle.
- A saggy bum has too much loose skin for its volume. The buttock hangs over a lengthened crease, and adding volume alone can make it hang lower. The fix is a buttock lift, sometimes with volume added.
A widely used classification separates pseudo-ptosis, where the buttock sits in a normal position, from true ptosis, where the buttock itself has dropped, and in the study that introduced it, weight gain, ageing and weight loss were all linked to more severe drooping[3]. A simple check: stand side-on to a mirror. A flat bum with a short crease and firm skin needs volume; a lower bum folding over a long crease needs skin removed as well.
Dimpling is a separate issue. Cellulite dimples are caused by fibrous bands tethering the skin, and adding volume can make them more obvious. Centre for Surgery offers subcision, which releases those bands, and our guide on how to get rid of cellulite explains which treatments work.
What Is Flat Butt Syndrome (Dead Butt Syndrome)?
Flat butt syndrome (sometimes called flat buttocks syndrome), dead butt syndrome and gluteal amnesia are informal names, not medical diagnoses, for glutes that are slow to “switch on”. The idea is that long hours of sitting leave the glutes under-used, so the hamstrings and lower back take over. People describe a numb or achy buttock after sitting, outer hip pain, lower back or knee pain during exercise, and difficulty feeling the glutes work. Persistent outer hip pain is often gluteal tendinopathy, which needs assessment by your GP or a physiotherapist, not cosmetic surgery.
Can sitting too much give you a flat bum? Sitting does not squash buttock fat flat or change your frame. Long periods of inactivity can mean weaker glutes and a less lifted upper bum, but there is little direct evidence that sitting alone causes a flat bum. Break up sitting with short walks and keep the glutes strong. If one side looks flatter, our guide to uneven buttocks and glute imbalance explains why.
Does running give you a flat bum, and does cycling make your bum flat? Not directly, but endurance exercise burns buttock fat and builds little glute size.
Flat Bum Exercises: Can You Fix a Flat Bum With Exercise?
Partly. Exercise builds the gluteal muscles, which adds some lift and roundness, especially to the upper buttock. It cannot add fat, change your pelvis or tighten loose skin.
The most effective flat bum exercises, the core of any flat butt workout, load the glutes heavily through hip extension. A 2023 randomised trial using MRI scans, published in Frontiers in Physiology ↗, found that 9 weeks of hip thrusts or back squats produced similar growth in the gluteal muscles, although squats also built the thighs more[4]. A systematic review of muscle activity found the highest glute activation during step-ups, followed by hip thrusts, deadlifts, lunges, split squats and squats[5].
A practical plan for building a flat bum:
- Train the glutes two or three times a week with hip thrusts, step-ups, Romanian deadlifts, split squats and lunges.
- Add load progressively. Bodyweight bridges help beginners, but muscle grows when the weight or repetitions keep increasing.
- Include side work such as banded side steps for the upper outer glutes.
- Eat enough protein and calories. Muscle is hard to build in a large calorie deficit.
Exercise suits someone whose flat bum is mostly muscle. If you train hard and your bum is still flat, fat or frame is usually the reason. Our comparison of BBL vs squats explains what glute training can and cannot achieve.
How Long Does It Take to Fix a Flat Bum?
It depends on the method:
- Glute training: muscle growth was measurable on MRI after 9 weeks[4], but a visible change in shape usually takes several months, and you need to keep training to keep it.
- Liquid BBL: visible straight away, with swelling or bruising for 2 to 5 days, lasting around 12 to 18 months.
- BBL: swelling peaks at 3 to 5 days, the buttocks soften (“fluff”) at 6 to 8 weeks, most of the result shows at 3 months and the final shape settles at 3 to 6 months.
- Buttock implants: the shape is there from the start and settles over the following months; exercise waits until 8 weeks.
- Buttock lift: the lift is immediate, and the scar fades over the following year.
How to Fix a Flat Bum Without Surgery
If you want to know how to get rid of a flat bum without an operation, there are three realistic forms of flat bum treatment: glute training, which works if the main problem is muscle; high-waisted, structured jeans or shaping underwear, which change how a flat bum looks in clothes; and a liquid BBL, which adds a modest amount of volume with no downtime. Creams, supplements, vacuum devices and massagers do not add lasting volume.
At Centre for Surgery, the non-surgical butt lift (liquid BBL) uses HYAcorp hyaluronic acid body filler only, injected by surgeons in a sterile theatre under ultrasound guidance with local anaesthetic, in 45 to 60 minutes. One to three sessions may be needed, you avoid direct pressure on the buttocks for 24 to 48 hours, and the result lasts around 12 to 18 months. The filler can be dissolved with hyaluronidase. It suits small corrections such as hip dips.
Who injects matters. In August 2025 the Department of Health and Social Care announced that the highest-risk non-surgical procedures, including non-surgical BBLs, should only be done by qualified healthcare professionals at CQC-registered providers, and on 21 October 2026 it proposed that fillers injected anywhere other than the face be legally defined as cosmetic surgery, so only doctors could perform them (GOV.UK announcement ↗). Never accept liquid silicone or unnamed “butt injections”.
Flat Bum Surgery: BBL, Implants or Buttock Lift?
Surgery is the only way to add substantial volume to a flat bum or remove loose skin. The right operation depends on which layer is the problem and how much spare fat you have.
| Option | What it fixes | Donor fat needed | Recovery | Complication data |
|---|---|---|---|---|
| Glute exercise | Muscle only | None | No downtime; results take months | Very low risk with sensible progression |
| Liquid BBL (HYAcorp) | Fat layer, modest volume; lasts 12 to 18 months | None | No downtime; no direct pressure for 24 to 48 hours | Little long-term published data; reversible with hyaluronidase |
| Mini or skinny BBL | Fat, modest volume | Mini: 800 to 1,000 ml from 2 areas; skinny: small amounts from 4 or 5 areas | Mini: about 1 week off, exercise from 4 weeks; no sitting on the buttocks for 2 weeks | Fat grafting: 6.8% pooled complication rate[6] |
| BBL | Fat and shape, plus a slimmer waist from the liposuction | 1,600 to 2,000 ml; BMI about 23 to 28 ideal | 1 to 2 weeks off; no sitting on the buttocks for 2 weeks; full exercise from 6 weeks | Fat grafting: 6.8%[6]; fat embolism risk rises with injection into muscle[7] |
| Buttock implants | Projection where there is too little fat; disguises a flat frame | None (fat can be layered over) | About 2 weeks off; cushion for 8 weeks; exercise from 8 weeks | Implants: 31.4% pooled complication rate[6]; lower with intramuscular placement[8] |
| Buttock lift | Loose skin; adds volume only if combined with fat or auto-augmentation | None (optional fat transfer) | Operation 2 to 3 hours; permanent scar in the swimwear line | Mainly wound-healing problems along the scar; rates vary with technique and weight history |
No treatment changes the bones of the pelvis; fat and implants can only disguise a flat frame by adding volume over it.
Flat bum BBL: fat transfer for a flat bum
For most people with enough spare fat, a BBL is the most natural way to round out a flat bum. Fat is taken by liposuction from areas such as the tummy, flanks and back, which also narrows the waist, then purified and injected into the buttocks. A 2019 systematic review of 4,362 patients in Annals of Plastic Surgery ↗ found complications in 6.8% of fat grafting patients, compared with 23.1% for flap techniques and 31.4% for implants[6].
The serious risk of a BBL is fat embolism, when fat enters the large veins in or under the buttock muscle. The 2017 ASERF task force report in Aesthetic Surgery Journal ↗, covering 198,857 gluteal fat grafting cases, found that injecting into the deep muscle was linked to significantly more fatal and nonfatal fat emboli[7], and later guidance recommended ultrasound to confirm where the cannula sits[9]. At Centre for Surgery, fat is placed only in the layer under the skin, above the gluteal muscle, never into or beneath it, under real-time ultrasound guidance on every BBL. Our article on ultrasound-guided BBL explains why this matters.
A BBL is a day case under TIVA (total intravenous anaesthesia) and takes 3 to 4 hours. You avoid sitting directly on your buttocks for 2 weeks, wear a compression garment on the donor areas for 6 weeks and return to full exercise at 6 weeks. For mild skin laxity, Argo Plasma is usually the preferred skin-tightening treatment alongside a BBL, and BodyTite is also available; see Argo Plasma skin tightening. A BBL is never done in the same operation as a tummy tuck or breast fat transfer at Centre for Surgery; these are planned separately.
For a smaller change, a mini BBL transfers 800 to 1,000 ml from two areas in around 2 hours. Men with a flat bum usually want a squarer, more projected shape, which is planned differently in a male BBL.
Buttock implants for a flat bum
Buttock implants suit people with too little spare fat for a BBL, or who want more projection than fat alone gives. Solid silicone implants of 200 to 600cc are placed within the gluteal muscle through a single incision hidden in the cleft between the buttocks, in 1 to 2 hours as a TIVA day case. A 2025 meta-analysis of 2,682 patients in Plastic and Reconstructive Surgery ↗ found lower complication rates with intramuscular and submuscular placement than with placement just under the muscle covering, and an overall implant removal rate of 1.05%[8]. Recovery is longer than after a BBL, and fat can be layered over the implants to soften the edges.
Buttock lift for a flat, saggy bum
A buttock lift removes loose skin and repositions the buttock, which often makes a deflated bum look fuller at the top. It does not add volume on its own, so it can be combined with fat transfer or auto-augmentation, where your own tissue is turned in to add shape. It leaves a permanent scar in the swimwear line, and your weight should be stable for 6 to 12 months first.
What If You’re Too Slim for a BBL?
A slim build is a common reason for a flat bum. At Centre for Surgery, a BMI of about 23 to 28 is ideal for a standard BBL, and the upper limit is a BMI under 30. Below a BMI of 23, a skinny BBL gathers small amounts of fat from four or five areas, such as the tummy, flanks, lower back and inner thighs, for a modest, proportionate result.
If there is too little fat even for a skinny BBL, implants, implants combined with fat, or a liquid BBL can add shape instead. Gaining weight to qualify is generally not advised: if you lose it afterwards, the transferred fat shrinks and the result goes with it. Our guide on what happens if you don’t have enough fat for a BBL explains how surgeons assess donor fat.
Flat Bum Before and After
These are real Centre for Surgery patients, blurred by default; tap to reveal.
Real Centre for Surgery patient, photographed at least six months after BBL surgery.
Real Centre for Surgery patient, BBL side view. Individual results vary.
The side view shows the change most clearly, as projection is what a flat bum lacks. Results depend on your frame, skin and how much fat survives, typically 50 to 70% of what is transferred. More real results are in our BBL before and after photos gallery.
Frequently Asked Questions
How do you go from a flat bum to a round bum?
Work out which layer is missing. If it is muscle, progressive glute training two or three times a week adds roundness over several months. If it is fat, you need added volume, usually a BBL if you have enough spare fat, or implants or filler if you do not. Loose skin needs a buttock lift.
My bum is flat: how do I make it bigger?
Build the gluteal muscles with heavy, progressive exercises that work hip extension, such as hip thrusts, Romanian deadlifts, split squats and step-ups, and eat enough protein. Training builds muscle, not fat, so it helps most when weak glutes are the main cause.
How can I get fuller buttocks naturally?
Glute training is the only natural way to add lasting size, and it works by building muscle. Keeping a stable weight helps too, as buttock fat shrinks when you lose weight. Creams, supplements and massagers do not add volume. For more fullness than training can give, fat transfer uses your own tissue.
How do I get my buttocks back after weight loss?
Start with strength training to rebuild the glute muscle. Once your weight has been stable for at least 3 months, or 6 to 12 months after major weight loss, a BBL can restore volume if you have spare fat, and a buttock lift can remove loose skin. Many people need both.
How should you sit to avoid a flat bum?
How you sit does not change the shape of your bum, but sitting for hours leaves the glutes inactive. Get up and walk for a few minutes every half hour or so, keep your weight even on both sides, and do a few glute squeezes or bridges during the day.
What are the signs of weak glutes?
Common signs include knees that roll inwards when you squat or climb stairs, a hip that drops on one side as you walk, lower back or outer hip pain during exercise, and difficulty feeling the glutes work during bridges. Persistent hip pain should be assessed by a GP or physiotherapist.
How do you fix dead butt syndrome?
Break up long periods of sitting and strengthen the glutes with bridges, clamshells, banded side steps and hip thrusts. Stretching the hip flexors at the front of the hip often helps. Outer hip pain that does not settle may be gluteal tendinopathy, which a physiotherapist can treat.
Does walking strengthen the glutes?
Walking keeps the glutes active and counters long hours of sitting, and uphill walking and stair climbing work them harder. On its own, walking does not give enough resistance to build much glute size, so add resistance exercises to change the shape of a flat bum.
Flat Bum Surgery in London
Flat bum surgery at Centre for Surgery is performed by GMC-registered surgeons at our CQC-regulated Baker Street hospital, rated Good overall by the CQC. We offer the Brazilian butt lift, mini and skinny BBL, male BBL, buttock implants, buttock lift and the non-surgical liquid BBL, and your surgeon will assess your frame, fat, muscle and skin to recommend the option that fits. Every BBL is performed under real-time ultrasound guidance with fat placed only above the muscle, and the consultant who assesses you is the consultant who performs your surgery. We recommend a two-week cooling-off period before you go ahead. Your initial consultation is £100, redeemable against the cost of surgery if you go ahead. Current prices are in our BBL cost guide. Finance isn’t available for BBL, buttock implants or the non-surgical butt lift at Centre for Surgery, so these procedures are self-funded.
Phone: 020 7993 4849 | Address: 95–97 Baker Street, Marylebone, London W1U 6RN
Contact us to schedule a consultation
References
- Mendieta CG, Sood A. Classification system for gluteal evaluation: revisited. Clinics in Plastic Surgery 2018;45(2):159–177. doi:10.1016/j.cps.2017.12.013 ↗
- Hoenig JF, Swetje K. Age-related ptosis of the buttock: an anthropometric gender-specific analysis. Aesthetic Plastic Surgery 2013;37(6):1090–1099. doi:10.1007/s00266-013-0205-2 ↗
- Gonzalez R. Etiology, definition, and classification of gluteal ptosis. Aesthetic Plastic Surgery 2006;30(3):320–326. doi:10.1007/s00266-005-0051-y ↗
- Plotkin DL, Rodas MA, Vigotsky AD, et al. Hip thrust and back squat training elicit similar gluteus muscle hypertrophy and transfer similarly to the deadlift. Frontiers in Physiology 2023;14:1279170. doi:10.3389/fphys.2023.1279170 ↗
- Neto WK, Soares EG, Vieira TL, et al. Gluteus maximus activation during common strength and hypertrophy exercises: a systematic review. Journal of Sports Science and Medicine 2020;19(1):195–203. PMC7039033 ↗
- Asserson DB, Kulinich AG, Orbay H, Sahar DE. Differences in complication rates of gluteoplasty procedures that utilize autologous fat grafting, implants, or local flaps. Annals of Plastic Surgery 2019;82(5S Suppl 4):S342–S344. doi:10.1097/SAP.0000000000001765 ↗
- Mofid MM, Teitelbaum S, Suissa D, et al. 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 ↗
- Elsaftawy A, Bonczar M, Jagosz M, Ostrowski P. Complications following primary implant-based gluteal augmentation: a systematic review and meta-analysis. Plastic and Reconstructive Surgery 2025;156(6):894–907. doi:10.1097/PRS.0000000000012213 ↗
- Del Vecchio D, Kenkel JM. Practice advisory on gluteal fat grafting. Aesthetic Surgery Journal 2022;42(9):1019–1029. doi:10.1093/asj/sjac082 ↗
Related Articles
- How to Get Rid of Saggy Buttocks
- BBL vs Squats: Can Glute Training Give You a BBL Shape?
- Ozempic Butt: What It Is, Why It Happens and How to Fix It
- BBL vs Butt Implants: Which Is Better for You?
