By Pat Anson, PNN Editor

Fibromyalgia patients with obesity experienced a significant reduction in pain and other symptoms after three weeks on a strict low-calorie diet, according to a new study that suggests limiting calories – not just weight loss – can have an analgesic effect.

Researchers enrolled nearly 200 patients diagnosed with fibromyalgia who were participating in a weight management program at the University of Michigan Health System. Participants had an average body mass index (BMI) of 41, which is considered severe obesity.

For 12 weeks, they were put on a very low energy diet (VLED) that limits bread, rice, potatoes and other foods that are high in carbohydrates. VLED is designed to shift the body away from using glucose in sweet or starchy foods to burning its own body fat for energy. Study participants were limited to just 800 calories a day, less than half the amount recommended for adult women and only a third of the amount recommended for men.

After just three weeks on the restricted diet, nearly three out of four participants (72%) experienced symptom reductions of 30% or more, regardless of the amount of weight lost. Patients who showed little or no improvement had a higher BMI at the start of the study and were more likely to have had a diagnosis of depression.

“Our results show, for the first time, that individuals following aggressive calorie restriction, ie, a VLED, had rapid and significant improvements in pain distribution and common pain-related comorbid symptoms and, importantly, prior to the achievement of significant weight loss,” researchers reported in the journal ACR Open Rheumatology.

“Furthermore, improvement at week 3 was strongly associated with improvement over the entire 12-week course of VLED, suggesting that patients who respond are likely to show these effects early in the process. These findings provide preliminary support for the hypothesis that calorie restriction, per se, can reduce pain and comorbid symptoms in individuals with obesity.”

Fibromyalgia is a poorly understood disorder characterized by widespread body pain, fatigue, poor sleep and depression. The FDA has approved three drugs to treat fibromyalgia -- duloxetine (Cymbalta), milnacipran (Savella) and pregabalin (Lyrica) -- but many patients say the drugs are ineffective and often have side effects.  

Previous studies have suggested that weight loss can help lower pain levels, but the improvement was thought to be caused by reduced stress on knees, hips and lower back – parts of the body that are weight-bearing.  

The new study suggests that a strict diet alone can significantly reduce fibromyalgia pain without major weight loss, but researchers caution that more studies are needed to fully understand the biological processes at work.

“The implications of this study suggest an early association between caloric restriction, through a VLED, and fibromyalgia symptoms. Although a larger study with a control group would be the next step in investigating this association, this provides important information for clinicians who counsel patients on alternatives to pharmacologic treatments for pain and other somatic symptoms,” researchers concluded.     

Many previous studies have shown that a low calorie diet can help reduce pain levels. A 2018 study at the University of Michigan found that obese patients on a low-calorie liquid diet for 12 weeks not only had lower pain levels in their knees and hips, but also in unexpected areas such as the abdomen, arm, chest and jaw. Study participants who lost 10% of their weight also reported better mental health, improved cognition and more energy.