Uterine fibroids are non-cancerous growths that develop from the muscle tissue of the uterus. These growths are extremely common, and for many women, the answer to whether they can cause weight gain is yes. The increase in weight or size is rarely due to metabolic changes or fat accumulation. Instead, it is primarily caused by the physical mass of the fibroids themselves or by secondary symptoms that cause fluid retention and abdominal swelling.
Understanding Uterine Fibroids
Uterine fibroids, also known as leiomyomas, are solid masses composed of smooth muscle and fibrous tissue. They can range dramatically in size, sometimes being as small as a seed or as large as a melon. Fibroids are classified by their location, including submucosal (under the uterine lining), intramural (within the uterine wall muscle), and subserosal (on the outside surface of the uterus).
These growths are highly dependent on reproductive hormones, specifically estrogen and progesterone, and are most prevalent during a woman’s reproductive years. Affecting up to 80% of women by age 50, fibroids typically shrink naturally once a woman enters menopause and hormone levels drop significantly.
The Direct Impact of Fibroid Mass on Weight
The most direct way fibroids cause weight gain is through their physical mass. While smaller fibroids may only weigh a few grams, large or numerous fibroids can represent a significant physical burden. A large single fibroid or a cluster of many fibroids can easily weigh several pounds, and rare cases have documented masses weighing 25 pounds or more.
As the fibroids grow, the uterus expands to accommodate the volume, leading to a noticeable increase in abdominal girth. This growth can cause the abdomen to protrude, often giving the appearance of being pregnant, a phenomenon sometimes termed a “fibroid belly.” This weight gain is purely the added weight of the tissue mass, distinct from an increase in body fat.
Indirect Symptoms That Mimic Weight Gain
Beyond the actual mass of the fibroids, several related symptoms can make a person feel or appear heavier. A common complaint is bloating and abdominal distension, caused by large fibroids putting pressure on surrounding organs in the pelvic cavity. The enlarged uterus can compress the colon, leading to bowel disturbances and chronic constipation. This pressure causes temporary bulk and discomfort, contributing to a visibly larger midsection. Similarly, pressure on the bladder can lead to urinary retention, further adding to the abdominal swelling.
Another indirect mechanism involves the heavy menstrual bleeding associated with fibroids. Profuse blood loss can lead to iron deficiency anemia, resulting in profound fatigue and lethargy. This fatigue often decreases a person’s motivation and ability to maintain regular physical activity, leading to a sedentary lifestyle and genuine metabolic weight gain from reduced caloric expenditure.
Treatment Options for Fibroid-Related Bulk and Symptoms
The only way to fully reverse the weight and bulk caused by fibroid mass is through treatment that causes shrinkage or removal. Medications can be used to manage symptoms or reduce fibroid size temporarily. Gonadotropin-releasing hormone agonists (GnRHa) can shrink fibroids by up to 50% to 60% by creating a temporary, menopause-like state that limits hormone flow.
Minimally invasive procedures offer options that preserve the uterus. Uterine Fibroid Embolization (UFE) involves blocking the blood vessels that supply the fibroids, causing them to shrink by an average of 30% to 50%. Radiofrequency ablation uses heat energy to destroy the fibroid tissue, leading to a reduction in size and symptom resolution.
For large, symptomatic fibroids, surgical removal may be necessary. A myomectomy removes only the fibroids, preserving the uterus for women who wish to retain their fertility. For women finished with childbearing, a hysterectomy, which removes the entire uterus, is a definitive surgical solution that resolves the weight and bulk permanently.