The gluteal muscles, commonly called the glutes, are a group of three distinct muscles—the gluteus maximus, gluteus medius, and gluteus minimus—that form the shape and mass of the buttocks. The gluteus maximus is the largest, functioning as a major hip extensor. The medius and minimus muscles stabilize the pelvis and control leg movement. A noticeable loss of volume is often a result of changes in muscle mass, fat distribution, or a combination of both.
Daily Habits and Muscle Inactivity
The most common reason for a loss of gluteal volume is extended periods of inactivity, often described as disuse atrophy. When muscles are not regularly challenged, the body breaks down the tissue, perceiving the muscle as unnecessary to maintain. This process is accelerated by a sedentary lifestyle, where many hours spent sitting keep the gluteal muscles in a lengthened, relaxed state.
This chronic deactivation can lead to “Gluteal Amnesia” or “dead butt syndrome,” where the gluteus medius muscle fails to activate efficiently. Tight hip flexor muscles, caused by prolonged sitting, inhibit the action of the glutes. The gluteal muscles essentially “forget” their primary role in stabilizing the pelvis and supporting proper alignment.
Poor sitting posture, such as tucking the pelvis under, further contributes to this problem by minimizing the engagement of the gluteal muscles. Over time, this muscle imbalance forces other muscles, like the hamstrings and lower back muscles, to compensate for the weak glutes, leading to potential pain in the hips, knees, and lower back. It can take nearly twice as long to restore the strength and activation of these muscles with exercise as it took for the atrophy to occur.
Weight Changes and Nutritional Deficiencies
The appearance of a flatter backside is not solely due to muscle loss, as the buttocks contain a significant layer of subcutaneous fat. When a person loses a substantial amount of weight, especially through rapid dieting or bariatric surgery, the shrinking of fat cells in the gluteal region causes a noticeable reduction in volume. A fast decrease in volume may also leave the skin stretched and loose, creating a “deflated” appearance.
Weight loss almost always results in a reduction of both fat mass and lean muscle mass. When the body is in a calorie deficit, it draws energy from both fat stores and muscle tissue. This process is called catabolism, which is the breakdown of complex molecules like muscle protein to release energy.
The risk of muscle loss is significantly higher with inadequate protein intake. Protein is the primary building block for muscle tissue, and without sufficient amounts, the body breaks down existing muscle for necessary amino acids. Prioritizing protein consumption and incorporating strength training are important strategies to preserve muscle mass while losing body fat.
Natural Biological Shifts
Muscle loss is an inevitable part of the aging process, known as sarcopenia, which involves the progressive loss of muscle mass and strength. While muscle mass generally peaks in a person’s twenties and thirties, the decline begins around age 30 and accelerates later in life. This age-related loss affects all skeletal muscles, including the glutes, reducing both size and quality of the tissue.
Changes in hormone levels also influence fat storage and muscle maintenance. For instance, hormonal shifts during menopause can lead to a redistribution of fat from the lower body to the abdomen. This change, combined with sarcopenia, contributes to the flattening of the glutes and a shift in overall body shape.
Furthermore, with age, there is often an increase in intramuscular adipose tissue (IMAT), which is fat infiltration within the muscle fibers. This process, sometimes called fatty atrophy, reduces the quality and functional strength of the muscle. This impairment occurs even if the muscle size does not shrink drastically, further affecting the glutes’ stabilizing and movement roles.
When to Consult a Doctor
While most changes in gluteal volume are related to lifestyle factors, diet, or the natural aging process, certain symptoms warrant a medical evaluation. Consulting a doctor is advised if you notice a sudden, rapid, and unexplained loss of muscle mass, or atrophy, in one or both buttocks. Sudden atrophy could be a sign of a more serious underlying medical issue that requires diagnosis and treatment.
It is also important to seek professional medical advice if the muscle loss is accompanied by neurological symptoms. These symptoms include new or worsening pain, persistent numbness, or a tingling sensation that radiates down the legs. Such signs can indicate conditions like localized nerve impingement, such as severe sciatica, or a progressive neurological disease that is affecting the nerves that control the gluteal muscles.