A B belly gets its name from the horizontal crease that runs across the midsection, dividing the stomach into an upper and lower section so it resembles the letter “B” when viewed from the side, rather than the smooth rounded “D” shape many people expect. The crease is not a medical condition in itself. It results from a combination of how your body stores fat, the structure of the connective tissue beneath your skin, and sometimes factors like posture, bloating, or weakened abdominal muscles. Because multiple things contribute to the shape, there is no single fix, but there are real options depending on what is driving it for you.
Why the Crease Forms in the First Place
The fat beneath your abdominal skin is not one uniform slab. It is organized into distinct layers separated by sheets of connective tissue called fascia. Anatomical studies show that the subcutaneous tissue of the abdomen has at least three layers: a superficial fat layer near the skin, a fibrous membrane in the middle, and a deeper fat layer closer to the muscle wall. The deeper layer has large, flat lobes of fat cells oriented mostly horizontally, while the superficial layer has rounder, more compact lobes. These layers vary in thickness from person to person and from one part of the abdomen to another.1PubMed. Layers of the abdominal wall: anatomical investigation of subcutaneous tissue and superficial fascia
The crease itself typically sits at or near the navel, where the fascia anchors more firmly to the underlying muscle. Research on abdominal fascia confirms that the superficial fascia is multilayered in the midline and thins out as it moves to the sides, and that fat lobules differ in shape, size, and arrangement depending on location.2PubMed Central. Anatomical study of superficial fascia and localized fat deposits of abdomen Where fascia attaches tightly, it creates a natural tethering point. If fat accumulates above and below that anchor, the flesh on either side puffs outward while the tethered zone stays indented, and you get two distinct bulges instead of one smooth curve.
This is why two people at the same weight can carry their stomach very differently. One person’s fascia might tether loosely, producing a round belly, while another’s holds firm at the midline, producing the B shape. Genetics play a big role in where and how your fascia attaches, which is also why B bellies tend to run in families even when body weight varies widely among relatives.
How Fat Distribution Differs Between the Upper and Lower Abdomen
Not all belly fat behaves the same way. The fat stored just under the skin, which makes up the visible belly shape, is structurally and metabolically different from the deeper fat packed around your organs. The deeper fat, often called visceral fat, is more metabolically active, more responsive to stress hormones, and more prone to expanding under certain hormonal conditions.3PubMed. Subcutaneous and visceral adipose tissue: structural and functional differences Visceral fat sits behind the abdominal wall and tends to push the upper abdomen outward, contributing to the upper bulge of a B belly.
The lower abdomen, by contrast, tends to accumulate subcutaneous fat, which is softer and sits closer to the surface. This lower pouch often feels squishier than the firmer upper region. The combination of a visceral-fat-driven upper bulge and a subcutaneous-fat-dominated lower pouch, separated by that fascial tether, is the classic anatomy of a B belly. Understanding this distinction matters because the two types of fat respond differently to diet, exercise, and even stress.
The Role of Hormones and Stress
Cortisol, the body’s primary stress hormone, has a well-documented relationship with abdominal fat. Women with more central fat distribution secrete more cortisol during stressful situations, and that cortisol in turn promotes further fat storage in the midsection.4PubMed. Stress-induced cortisol response and fat distribution in women This creates a feedback loop: stress leads to cortisol, cortisol encourages visceral fat accumulation, and that visceral fat pushes the upper abdomen outward, deepening the B-belly crease.
Elevated cortisol at either the whole-body level or locally within fat tissue itself drives the preferential expansion of central fat deposits, especially the visceral kind.5PubMed Central. Deconstructing the roles of glucocorticoids in adipose tissue biology and the development of central obesity Even in younger populations, stress has been linked to increases in both visceral and subcutaneous abdominal fat, with the effect being strongest in people whose cortisol response is already elevated.6PubMed Central. Stress and abdominal fat: preliminary evidence of moderation by the cortisol awakening response in Hispanic peripubertal girls
Estrogen also plays a major part. During the years around menopause, declining estrogen levels trigger a shift in where the body stores fat. Estrogen normally encourages fat storage in the hips and thighs and under the skin; as it drops, fat migrates toward the abdomen, particularly the visceral compartment.7PubMed Central. Adverse Changes in Body Composition During the Menopausal Transition and Relation to Cardiovascular Risk: A Contemporary Review This redistribution can cause someone who never had a B belly to develop one in their late forties or fifties, even without gaining weight overall. It also helps explain why B bellies become more common with age, particularly in women.
Diastasis Recti and Abdominal Wall Weakness
If the two halves of the rectus abdominis muscle (the “six-pack” muscle) separate along the midline, the result is a condition called diastasis recti. The tissue connecting the two sides, called the linea alba, stretches and thins, creating a gap. That gap lets the abdominal contents push forward, producing a visible bulge that often sits right at or above the navel.8Current Women’s Health Reviews. Diastasis Recti Abdominis-diagnosis, Risk Factors, Effect on Musculoskeletal Function, Framework for Treatment and Implications for the Pelvic Floor
Pregnancy is the most common trigger. In one study of first-time mothers at six to eight months postpartum, about one in five reported visible bulging along the abdominal midline consistent with diastasis recti.9PubMed Central. Diastasis recti abdominis: A comprehensive review But pregnancy is not the only cause. Significant weight gain, repeated heavy lifting with poor form, and aging can all stretch the linea alba enough to produce a similar separation. When diastasis recti is present, it tends to worsen the B-belly appearance because the weakened midline sags outward unevenly, often accentuating that horizontal crease.
Research in animal models suggests that the abdominal wall does remodel after pregnancy, with strength and stiffness increasing in the early postpartum period.10PubMed. Postpartum biomechanical adaptations of the anterior abdominal wall in a rat model: Implications for diastasis rectus abdominis So some degree of natural recovery happens, but for many people the recovery is incomplete, leaving a residual gap that exercises or surgery may need to address.
Bloating Can Make a B Belly Look Worse
A B belly often looks more pronounced at certain times of day, and bloating is usually the reason. Functional bloating involves both a subjective feeling of fullness and, in many cases, measurable distension of the abdomen. The distension appears to involve an abnormal coordination pattern where the diaphragm contracts downward while the abdominal wall muscles relax outward, pushing the belly forward.11PubMed Central. Abdominophrenic Dyssynergia: A Narrative Review That outward push does not distribute evenly when a fascial crease is present. Instead, the upper and lower sections inflate separately, making the B shape more dramatic.
Common causes of chronic bloating include dietary triggers, constipation, bacterial overgrowth in the small intestine, and heightened sensitivity of the gut nerves.12PubMed Central. A Practical Approach to the Diagnosis and Treatment of Abdominal Bloating and Distension If you notice your B belly fluctuates a lot between morning and evening, or gets much worse after meals, bloating is probably a significant contributor on top of whatever structural factors are at play.
Posture and Pelvic Tilt
The way you stand has a surprisingly large effect on how your belly looks. An anterior pelvic tilt, where the front of the pelvis drops and the lower back arches inward, pushes the lower abdomen forward and can make the lower bulge of a B belly more prominent. Studies on pelvic mechanics show that adopting a maximal anterior tilt increases the arch of the lower back by roughly 10 to 11 degrees.13PubMed. The effects of pelvic movement on lumbar lordosis in the standing position That exaggerated curve tilts the whole abdomen forward and downward.
Anterior pelvic tilt has also been linked to low back pain, which means fixing it can have benefits beyond appearance.14PubMed. Relationship between mechanical factors and pelvic tilt in adults with and without low back pain Pelvic tilting exercises, where you consciously tuck the pelvis under and flatten the lower back, can reduce this tilt and pull the lower belly back toward a more neutral position. It will not change how much fat is there, but it can change how that fat sits on your frame, which sometimes softens the B-belly appearance enough to make a meaningful visual difference.
The transversus abdominis, a deep corset-like muscle that wraps around the torso, is the abdominal muscle most consistently tied to managing intra-abdominal pressure.15PubMed. Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man When this muscle is weak or not engaging properly, the belly tends to protrude more. Strengthening it can help hold everything in tighter, which is why many of the exercise-based approaches for B bellies focus on deep core activation rather than traditional crunches.
Exercise Approaches That Actually Help
If diastasis recti is part of your picture, targeted deep core work can narrow the gap between the two sides of the muscle. A randomized controlled trial found that a deep core stability exercise program produced a statistically significant decrease in the distance between the rectus muscles in postpartum women, along with improvements in quality of life.16PubMed Central. Efficacy of deep core stability exercise program in postpartum women with diastasis recti abdominis: a randomised controlled trial These programs typically emphasize exercises like pelvic-floor contractions, transversus abdominis activation (the “drawing-in” maneuver), and slow, controlled movements that engage the deep core without bulging the belly outward.
Even virtual or at-home programs seem to work. One trial found that a remotely delivered exercise intervention significantly reduced diastasis width above the navel after several weeks of training.17PubMed Central. Postpartum Exercise Intervention Targeting Diastasis Recti Abdominis Interestingly, when researchers compared hypopressive exercises (a technique involving breath-holding and abdominal vacuum maneuvers) with conventional abdominal exercises for postpartum diastasis, both programs produced similar reductions in the gap.18PubMed Central. Effect of hypopressive and conventional abdominal exercises on postpartum diastasis recti: A randomized controlled trial The consistency of the exercise matters more than the specific method.
For fat reduction specifically, resistance training shows promise. A meta-analysis found that resistance training can reduce visceral fat on its own. But here is the part that trips people up: adding resistance training on top of a calorie deficit did not produce greater visceral fat loss than the calorie deficit alone.19PubMed. Effect of resistance training with and without caloric restriction on visceral fat: A systemic review and meta-analysis So if your goal is to reduce the fat contributing to the B shape, caloric balance is the dominant lever. Exercise supports it, builds muscle that holds the belly tighter, and improves health markers, but you cannot out-train a diet when it comes to visceral fat loss.
Dietary Strategies Worth Considering
If bloating is a significant contributor to your B belly, dietary changes can make a noticeable difference. The low-FODMAP diet, which limits certain fermentable carbohydrates that feed gas-producing gut bacteria, has promising evidence for reducing bloating. A systematic review and meta-analysis found that a low-FODMAP diet significantly reduced bloating severity in randomized controlled trials.20PubMed. Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis Additional research supports its potential in managing functional bloating and distension specifically.21PubMed Central. The low-FODMAP diet and the gluten-free diet in the management of functional abdominal bloating and distension
A low-FODMAP diet is meant to be temporary. You eliminate high-FODMAP foods (things like onions, garlic, wheat, certain fruits, and most legumes) for a few weeks, then systematically reintroduce them to identify your personal triggers. It is not a permanent eating plan, and it is best done with guidance from a dietitian so you do not unnecessarily restrict your diet long-term.
For the fat-loss component, the approach is more straightforward: a sustained, moderate calorie deficit. No particular macronutrient ratio targets belly fat preferentially. The body draws from fat stores according to its own genetic and hormonal priorities, and you cannot choose to lose fat specifically from the belly crease zone. But because visceral fat is metabolically active and sensitive to energy balance, it tends to respond relatively early in a weight-loss process. Many people notice their upper belly softens before their lower belly does, which can actually reduce the B-belly look before much overall weight has come off.
Non-Surgical Cosmetic Procedures
Several non-invasive devices have been cleared for reducing localized subcutaneous fat. Cryolipolysis (commonly known by the brand name CoolSculpting) freezes fat cells in a targeted area, causing them to die and be gradually cleared by the body. Clinical studies have shown it can reduce subcutaneous fat at the treatment site by up to about 25% after one session, with visible improvement in roughly 86% of treated subjects.22PubMed Central. Cryolipolysis for noninvasive body contouring: clinical efficacy and patient satisfaction
Other non-invasive options include radiofrequency devices, low-level laser therapy, and high-intensity focused ultrasound. A review of these technologies found that multiple devices are safe and effective for circumferential reduction of about 2 centimeters or more across the abdomen and other treatment areas, with no serious or permanent side effects reported.23PubMed. Non-invasive subcutaneous fat reduction: a review That said, the clinical effects are generally described as mild to moderate, typically in the range of 2 to 4 centimeters of circumference reduction over a full course of treatment.24PubMed Central. Review of the Mechanisms and Effects of Noninvasive Body Contouring Devices on Cellulite and Subcutaneous Fat
For a B belly specifically, these procedures can reduce the volume of the upper or lower bulge, but they cannot change the fascial tethering that creates the crease. If your crease is primarily structural, meaning the fascia is anchored firmly and the fat on either side is not excessive, non-invasive fat reduction may not dramatically change the B shape. It works better when excess subcutaneous fat is the main issue and the crease is relatively shallow.
Surgical Options
Abdominoplasty, or a tummy tuck, is the most direct surgical intervention for a B belly. The procedure removes excess skin and fat from the lower abdomen and typically includes plication, where the surgeon sutures the separated rectus muscles back together to tighten the abdominal wall. When diastasis recti is present, some surgeons now use mesh reinforcement instead of sutures alone. One study comparing the two approaches found that mesh repair had a lower rate of wound complications (0% versus 19% for standard plication), though both groups showed significant improvement in aesthetic scores.25PubMed Central. Mesh Repair of Rectus Diastasis for Abdominoplasty is Safer than Suture Plication
Liposuction can address localized fat deposits but comes with an important caveat. A controlled study found that while liposuction reduced body fat percentage in the treated area after six weeks, the overall body fat difference was no longer significant after one year. Fat that was removed from the thighs stayed gone, but fat reaccumulated in the abdominal region.26PubMed. Fat redistribution following suction lipectomy: defense of body fat and patterns of restoration The body appears to defend its total fat mass, and when fat is surgically removed from one area, it tends to come back elsewhere, often the abdomen. This means liposuction alone, without changes to diet and activity, may not be a lasting fix for a B belly.
When Clothing Creates or Worsens the Crease
Something rarely discussed in medical literature but extremely relevant in everyday life is the role of clothing, especially waistbands. Tight-waisted pants, jeans, and shapewear that sit at or near the navel press into the natural fascial tether point, essentially compressing the crease deeper and pushing fat above and below it outward. Research on clothing pressure confirms that the skin’s vertical deformation in the waist-abdomen region is significant, particularly when sitting, and that garment pressure interacts with the body’s natural contours in complex ways.27SAGE Journals (Journal of Engineered Fibers and Fabrics). Dynamic multidimensional pressure deformation in the waist-abdomen region of young women
High-waisted pants that sit above the crease, or lower-rise styles that sit well below it, tend to minimize the B appearance more than mid-rise waistbands that land right at the tether point. Stretchy, seamless fabrics distribute pressure more evenly than rigid denim or structured shapewear. Some people find that switching to high-waisted leggings with a wide, soft waistband makes a more immediate visual difference than weeks of exercise, simply because the garment is no longer digging into the one spot that creates the fold.
This is not a “fix” in any physiological sense, but for many people the B belly is primarily a cosmetic concern, and the most immediate solution to a cosmetic concern is often the simplest one. Choosing clothes that work with your body’s natural contours instead of against them is a valid, zero-risk approach that works the same day you try it.
Conditions That Mimic a B Belly
Not everything that looks like a B belly is caused by fat distribution and fascial anatomy. A few medical conditions can produce a similar appearance and are worth ruling out if your belly shape has changed suddenly or comes with other symptoms. Hernias, particularly umbilical or incisional hernias, can create a localized bulge that distorts the belly’s silhouette. Severe diastasis recti, as discussed earlier, produces a midline ridge or sag that can look like a crease from certain angles. Ascites, which is fluid accumulation in the abdominal cavity, can produce an unusually distended abdomen that hangs and folds differently than fat alone.
Lipedema, a condition involving abnormal fat deposition that disproportionately affects the legs but can also involve the torso, sometimes creates unusual contours that get mistaken for simple weight gain. And significant bloating from conditions like small intestinal bacterial overgrowth or gastroparesis can add inches to the belly in a pattern that accentuates a pre-existing crease. If your B belly appeared quickly, is painful, or is accompanied by digestive symptoms that are getting worse, it is worth seeing a doctor to make sure something more than anatomy and fat storage is going on.