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Possible Causes

Altered Metabolism

Despite your best efforts to eat healthy and stay active with fibromyalgia, you are frustrated with uncontrollable weight gain. Doctors dismiss your expanding waistline as a sign of inactivity, but you know there must be something else going on. After all, your inactive neighbors aren’t gaining weight, so why are you?

Increases in the immune system cytokine called IL-6, are okay for handling short-term situations such as healing your tissues. But when IL-6 is chronically elevated (as it is in fibromyalgia), this leads to undesirable changes in the way your body metabolizes glucose.

Insulin Resistance

When IL-6 is persistently elevated, it sends a nonstop signal to your pancreas to secrete more insulin. Over time, the chronically high insulin levels are not viewed with urgency. Eventually, this hormone becomes less effective in its ability to break down fat stores to deliver more blood glucose to exercising muscles. 

When your body becomes insensitive or resistant to the effects of insulin, you gain weight around the waistline. You also stockpile fats in your blood (such as triglycerides and cholesterol). Unless you take steps to treat this altered metabolic state, your fasting blood glucose values will rise to unhealthy levels. If your insulin remains above 100 mg/dL, you will end up with type 2 diabetes. In addition, elevations in noradrenaline with reduced adrenaline may lead to hypertension.

Fibromyalgia patients are four to five times more likely to exhibit signs of metabolic syndrome compared to healthy controls.1,2 Although your fibromyalgia symptoms make it harder to stay active, the inefficient way your body regulates glucose is at the heart of the problem. When you exercise, your body doesn’t break down fat stores to feed your muscles as it should. And when you restrict food intake, the fat stored around your waistline is not effectively broken down. 

Exercise should help build muscle mass, while dieting should aid with weight reduction and lead to a slimmer figure. Neither of these processes work as efficiently as they should when IL-6 is elevated and adrenaline is low. But there is more going on to tilt the scales towards increased fat deposits, both around the waist and in the muscles.

Your Weight Gain

Bjorn Gerdle, M.D., Ph.D., of Linkoping Sweden, has done the most extensive series of studies tying elevated immune system cytokines in the blood with abnormal fat deposits in your tissues.3 His research sets the record straight: your excessive fat deposits in the muscles and adipose tissues cannot be explained by increased body mass index or depressed mood. More specifically, he found increased cytokine levels (such as IL-6) and other metabolic products corresponded to the amount of increased fats deposits.

Gerdle conducted whole body scans to determine body composition (separating out the amount that is muscle, water and fat). He also sampled the contents of the general blood circulation as well as the composition of the blood flowing through muscles. And if that was not enough, he assayed the saliva to see if it might provide additional information. Most importantly, Gerdle’s team conducted all these tests on the same group of 32 fibromyalgia patients and 30 controls. Both groups were matched for age and body mass index or BMI. 

Ordinarily, researchers measure a handful of variables from a group of subjects and try to determine if there are any correlations between the different measures. Say, for example, a team finds elevated IL-6 in the blood and they notice that the fibromyalgia patients are more overweight (they have a higher BMI). Since fat cells can secrete IL-6, they may conclude that the patients have elevated IL-6 because they are overweight (i.e., they have more adipose tissue). But this is misleading because the researchers did not evaluate the whole body for fat deposits. If they had, they would have noticed unusual amounts of fat deposits in the muscles, not just around the waist.

It’s not normal for the body to dump excessive fat deposits in the muscles throughout the body. Gerdle found this to be the case for the fibromyalgia patients he evaluated. Yet the healthy controls with the same body mass index did not have a similar degree of muscle fat. This allowed Gerdle to definitively state that the increased cytokine levels and fat deposits were unrelated to BMI. Instead, his findings had to be due to abnormal immune and hormonal factors.

Okay, Gerdle’s work helps shed light on why you might struggle with weight gain, but what about your fibromyalgia pain? The higher the cytokine levels and the greater the amount of fat deposits, the greater the fibromyalgia patient’s pain. So, these alterations in your immune function and body composition are strongly tied to your pain.


Exercising muscles with excessive amounts of fat deposits can be more of a challenge, but if you continue to perform gentle movement on a regular basis, it should eventually help. It may be harder for you with fibromyalgia because your muscle mass is smaller due to the fat deposits, but it will help clear some of the toxic metabolic products from your muscles. Over time, the fat deposits should reduce, but it is a process that can’t be rushed without incurring a fibromyalgia flareup.

In the Diet & Nutrition section, we describe a radical weight loss program that leads to reduced pain in fibromyalgia. The presumption is that this low-calorie diet reduces the pain-promoting cytokines (like IL-6) secreted by the fat cells. But this is a drastic diet, so is there anything else you might be able to do?

Metformin is a drug prescribed for people with diabetes and metabolic syndrome. It helps them lose weight while combining it with exercise. The drug is also gaining attention for its potential to help people with chronic pain, even “fibromyalgia-like” pain.4 In addition to its favorable metabolic actions, metformin appears to have some ability to reduce cytokine-mediated inflammatory pain. It does have gastrointestinal side effects, but the drug has been on the market for years. If you are struggling to lose weight, you might ask your doctor about a trial of metformin.

  1. Loevinger BL, et al. Metab Clin Exp 56:87-93, 2007.
  2. Cakit O, et al. Arch Rheumatol 36(1):26-37, 2021.
  3. Gerdle B, et al. Frontiers Pain Res 2024 Jan. 18; 5:1288024. Free Journal Report
  4. Baeza-Flores, et al. Frontiers Pharmacol Sept 2020; 11:558474.