Uterine fibroids are common, non-cancerous growths that develop in the muscular wall of the uterus. Fibroids generally do not cause weight loss; in fact, the opposite is usually true. While a fibroid’s physical presence adds mass, noticeable weight changes are often related to abdominal expansion and secondary symptoms. Weight gain or the appearance of weight gain is the far more common scenario than losing weight.
What Uterine Fibroids Are
Uterine fibroids, also known as leiomyomas or myomas, are firm, rubbery masses composed of smooth muscle cells and fibrous tissue. They are common, affecting a large percentage of women by the age of 50, but many people never experience symptoms. These growths can vary significantly in size, ranging from tiny seedlings to large masses that can fill the entire abdominal cavity.
Fibroids are classified based on their location within the uterus, which dictates the type and severity of symptoms experienced. Intramural fibroids are the most common, growing within the muscular wall of the uterus, known as the myometrium. Subserosal fibroids grow on the outside of the uterus, sometimes pushing outward into the pelvic cavity. Submucosal fibroids are the least common type, developing just beneath the uterine lining and protruding into the uterine cavity, often causing the most significant bleeding symptoms.
Weight Gain or Abdominal Distension: The Common Scenario
The most frequent way fibroids impact body size is by causing the appearance of weight gain or actual weight increase, particularly in the abdomen. This effect is primarily due to the physical size of the fibroids themselves, often called the “bulk effect.” When fibroids are numerous or grow very large, they can physically enlarge the uterus, sometimes to the size of a five or six-month pregnancy, which causes the abdomen to distend.
This distended abdomen may feel firm and heavy, and it can cause clothing to fit differently. A large fibroid mass can weigh several pounds, directly contributing to overall body weight. The sheer presence of the growths can also press on surrounding organs, including the bladder and bowels.
Pressure on the digestive system can lead to secondary symptoms such as chronic constipation and bloating, further contributing to the perception of weight gain and abdominal fullness. Fluid retention, sometimes linked to hormonal fluctuations associated with fibroids, can also cause temporary increases in body weight. The pain and fatigue from fibroid symptoms can lead to reduced physical activity, which may indirectly contribute to fat accumulation over time.
Indirect Causes of Weight Loss
While fibroids do not directly stimulate weight loss through metabolic changes, a small number of people may experience unintended weight loss due to extreme secondary effects. This weight loss is considered an indirect consequence, driven by severe symptoms that interfere with normal caloric intake.
Large fibroids pressing on the stomach or intestines can create a sensation of fullness or discomfort, even after eating very little food. This pressure can lead to a significant reduction in appetite or a feeling of nausea, resulting in a lower caloric intake over time. When this reduction is prolonged, it can lead to unintentional, and sometimes unhealthy, weight loss.
Another indirect factor is severe, prolonged heavy menstrual bleeding, known as menorrhagia, which is a common symptom of fibroids. Chronic, heavy blood loss can cause iron-deficiency anemia, leading to extreme fatigue, weakness, and general malaise. In rare instances, this debilitating fatigue and overall poor feeling can contribute to a decreased desire to eat or prepare meals, potentially resulting in muscle wasting or weight loss. Unexplained or significant weight loss is a concerning symptom that always warrants a prompt medical evaluation to rule out other, potentially more serious, underlying health conditions unrelated to the fibroids.