Several biological factors contribute to differences in body shape across populations, including how and where the body stores fat, the curvature of the lower spine, and muscle-building tendencies in the lower body. Black men, on average, tend to carry more subcutaneous fat (the kind stored just under the skin) in the gluteal and hip region rather than around the internal organs. Combined with skeletal differences in pelvic tilt and spinal curvature, this can create a more prominent backside. But the full picture involves genetics, evolution, and a fair amount of stereotype that outpaces the actual variation between individuals.
Where the Body Stores Fat Matters
Not all body fat is created equal, and different populations tend to store it in different places. Research on people of African descent shows a pattern of carrying more subcutaneous fat, particularly in the gluteofemoral region (the buttocks and upper thighs), and less visceral fat, which is the deeper fat packed around internal organs. People of European descent, by contrast, tend to accumulate proportionally more visceral fat for the same overall body weight.
This isn’t just a cosmetic difference. Gluteofemoral fat is associated with a more favorable metabolic profile: lower LDL cholesterol, lower triglycerides, lower fasting glucose and insulin levels, and healthier blood pressure. Visceral fat, on the other hand, is linked to liver fat accumulation and greater cardiometabolic risk. So carrying weight in the hips and glutes rather than the midsection is, from a health standpoint, a protective pattern. The genetic signals that govern this fat distribution appear to involve differences in how fat cells in different depots are regulated at the molecular level, including variations in DNA methylation patterns within gluteal fat tissue itself.
Spinal Curvature and Pelvic Angle
Body shape isn’t only about fat. The skeleton underneath plays a major role in how the buttocks look from the outside. One key factor is lumbar lordosis, the natural inward curve of the lower spine. A greater degree of this curvature pushes the pelvis forward and the glutes backward, creating more visible projection even without additional fat or muscle.
Lumbar hyperlordosis, a more pronounced version of this curve, is documented more frequently in people of African descent. Plastic surgery literature on ethnic body proportions specifically notes that this spinal feature is a common and often desired characteristic in African American populations. The “projection ratio,” which measures how far the buttocks extend backward relative to a fixed skeletal landmark, tends to be higher when this curvature is more pronounced. So two people with identical amounts of gluteal muscle and fat can look quite different from the side based purely on how their spine and pelvis are angled.
Pelvic incidence, the angle at which the pelvis sits relative to the spine, also varies between individuals and populations. People with a higher pelvic incidence naturally develop more lower-back curvature to compensate, which tilts the buttocks into greater prominence. This is a structural, skeletal trait inherited from your parents, not something shaped by exercise or diet.
Muscle Response and Androgen Receptors
The gluteus maximus is one of the largest muscles in the human body, and how easily it grows varies from person to person. One important variable is androgen receptor content within muscle tissue. Research on resistance training found that people with higher androgen receptor density in their muscles experienced significantly more muscle growth from the same training program. Those with the most receptors gained the most lean body mass and the largest increases in muscle fiber size, for both slow-twitch and fast-twitch fibers.
This was true regardless of circulating hormone levels in the blood. In other words, it wasn’t about having more testosterone overall. It was about how sensitive the muscle cells themselves were to the hormones already present. While this specific research didn’t break results down by ethnicity, it helps explain why some men develop more gluteal muscle mass than others with the same activity level. Genetic variation in receptor density is one piece of that puzzle.
An Evolutionary Perspective
One theory for why populations originating in sub-Saharan Africa developed patterns of greater subcutaneous fat storage relates to the thermoregulatory demands of the open savannah. Early humans living on the East African plains faced scorching daytime heat but also surprisingly cold nights. Ground-level temperatures could drop below 12°C (about 54°F) due to intense radiative cooling, posing a real risk of hypothermia, especially for infants.
Researchers have proposed that natural selection favored individuals, particularly women, who carried more subcutaneous fat as insulation against nighttime cold. This fat also served as an energy reserve during food scarcity, which was critical during pregnancy and lactation. Storing that fat in the gluteal region rather than the abdomen would have preserved the body’s ability to shed heat during hot days while still providing insulation at night. Over tens of thousands of generations, populations adapted to these conditions retained genetic tendencies toward gluteofemoral fat storage.
Stereotype vs. Biological Reality
It’s worth separating measurable biological tendencies from cultural stereotypes. Real population-level differences in fat distribution and skeletal structure do exist, and they’re well documented in medical and anthropometric research. But these are averages across large groups, with enormous overlap between individuals of any background. Plenty of Black men have flat backsides, and plenty of white or Asian men have prominent ones.
Cultural beauty standards also shape perception. Research on body ideals across ethnic groups shows that African American aesthetic preferences have historically valued fullness in the buttocks and lateral hips, viewing these features as signs of vitality and attractiveness. Eurocentric beauty standards, by contrast, have traditionally emphasized thinness and minimized curvature. These differing standards influence what people notice, comment on, and remember, which can amplify the perception of difference beyond what biology alone accounts for.
The history of how Black bodies have been observed and described by Western science is also fraught. Researchers studying racialized body image have documented how physical characteristics common among Black people have been used to “mark” them as different, feeding stereotypes that reduce complex human variation to simplistic generalizations. The reality is more nuanced: body shape is shaped by a mix of genetics, diet, activity level, hormonal environment, and skeletal anatomy, all of which vary more within any racial group than between groups.