Fibromyalgia (FM) is a chronic disorder defined by widespread musculoskeletal pain, accompanied by profound fatigue and non-restorative sleep. A common observation among patients is an unexpected increase in body weight. The relationship between FM and weight gain is not a simple direct cause-and-effect, but rather a complex interplay of physical symptoms, prescribed treatments, and internal physiological changes.
Understanding the Complex Link Between Fibromyalgia and Weight
Fibromyalgia does not list weight gain as a primary diagnostic symptom, yet the prevalence of overweight and obesity is notably higher in this patient population than in the general public. Studies indicate that between 32% and 50% of individuals with FM are classified as obese, with an additional 21% to 28% being overweight. The weight gain experienced is often described as secondary, meaning it arises from the consequences of living with the condition, not the condition itself. The persistent physical symptoms of FM, particularly widespread pain and debilitating fatigue, directly interfere with maintaining a healthy lifestyle. Furthermore, the presence of excess weight can worsen the core symptoms of fibromyalgia, creating a negative feedback loop where increased pain leads to less activity, which in turn leads to further weight gain and symptom intensification.
Common Fibromyalgia Medications That Influence Metabolism
Medications used to manage fibromyalgia symptoms are a direct contributor to weight gain in the FM population. Drugs commonly prescribed, including certain classes of antidepressants and anticonvulsants, can alter metabolic processes and appetite regulation. The three medications approved by the Food and Drug Administration (FDA) for treating FM are Pregabalin, Duloxetine, and Milnacipran. Pregabalin, an anticonvulsant, is particularly well-known for its association with weight gain, involving increased appetite and changes in fat metabolism, with 9% to 15% of patients experiencing a clinically significant increase in body weight.
Certain tricyclic antidepressants (TCAs), sometimes used off-label for pain and sleep, can also cause weight gain by stimulating appetite. The other two FDA-approved medications, Duloxetine and Milnacipran, which are serotonin-norepinephrine reuptake inhibitors (SNRIs), have a more varied profile. Duloxetine is often considered weight-neutral, while Milnacipran is associated with weight stability or even modest weight loss.
How Pain and Fatigue Drive Lifestyle Shifts
Widespread pain and chronic fatigue lead to changes in daily behavior that promote weight gain. Constant pain and exhaustion make it challenging to maintain the physical activity levels necessary for calorie expenditure and metabolic health. As movement becomes difficult, individuals with FM adopt a more sedentary lifestyle, which significantly reduces calories burned. This reduced energy output, coupled with normal or increased food consumption, inevitably leads to a caloric surplus and subsequent weight gain.
The relentless nature of the illness can also trigger emotional or comfort eating as a coping mechanism for chronic distress and associated mental health issues. Highly processed, calorie-dense foods are often chosen due to their convenience and the temporary reward they provide. Difficulty performing physically demanding tasks like grocery shopping and cooking healthy meals also leads to a greater reliance on easily prepared, less nutritious options.
Hormonal Imbalance and Chronic Stress as Contributors
The chronic nature of fibromyalgia symptoms creates a state of perpetual physiological stress that affects the body’s internal systems. Living with constant pain and fatigue is a profound stressor, which can lead to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, the body’s primary stress response system. Chronic stress is often linked to sustained high cortisol levels, which promote the storage of visceral fat and increase the risk of developing insulin resistance.
Furthermore, the non-restorative sleep characteristic of FM disrupts the balance of appetite-regulating hormones. Poor sleep quality is known to decrease levels of leptin, the hormone that signals satiety, while increasing levels of ghrelin, the hormone that stimulates hunger. This hormonal shift makes a person feel less full after eating and more hungry overall, contributing to increased calorie intake and weight gain.