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Weight Loss Intervention May Relieve Joint Pain in Obese Patients

Studies demonstrate benefits of low-calorie intake and increased activity

With Andrew Schrepf, PhD, and Akiko Okifuji, PhD

Nearly 38% of American adults are obese,1,2 and when compared to adults of a healthy weight, substantially more also suffer from somatic symptoms such as pain, fatigue, cognitive impairment, sleep disorders, and depression.3,4 Many obese patients report pain in weight-bearing joints (particularly the hips and knees) and lower back.

A recent study5 examined how weight loss may affect this pain and other physical symptoms among 241 patients with obesity (BMI of at least 30). The weight-loss intervention was conducted at the Chronic Pain and Fatigue Research Center at the University of Michigan. Led by Amy Rothberg, MD, a clinical associate professor of internal medicine at the university, the research specifically examined the spatial distribution of pain, symptom severity (eg, fatigue, sleep difficulties), depression, and total fibromyalgia scale scores in 157 qualified obese patients who completed a 12- to 16-week weight-loss intervention. The intervention involved a very low-calorie diet (800 kcal/d) in the form of total liquid meal replacement. Patients enrolled in the program were also encouraged to gradually increase their physical activity levels via time and intensity.

Decline in Pain Symptoms

In addition to demographic data and medical background of the participants, investigators assessed the spatial distribution of pain and somatic symptoms. Researchers used the American College of Rheumatology (ACR) preliminary diagnostic criteria for fibromyalgia (FM) and the ACR modified criteria, including the Widespread Pain Index (WPI) and the Symptom Severity Index (SSI), which measured symptoms considered to be part of the centralized pain continuum, such as fatigue, non-refreshing sleep, cognitive difficulties, depressed mood, abdominal pain, and headaches. Depression was assessed using a 30-item Inventory of Depressive Symptomatology (IDS). Fasting blood serum was collected at baseline and after weight loss to assess differences in specific cytokines known to have pro-inflammatory as well as regulatory effects: interleukin (IL)-6,1β, 10, tumor necrosis factor (TNF)-α, and interferon (IF)-γ, as well as C-reactive protein (CRP).

Two-thirds of the patient sample were female, and 80% of the participants lost at least 10% of their body weight, with an average weight loss from baseline of 16.05%. Weight loss was associated with significant declines from baseline in symptom severity, depression, and fibromyalgia scores, and 56% of participants had at least a one-point increase in physical activity levels.5 Men showed greater improvement than women on scores for somatic symptoms and fibromyalgia symptoms. Greater weight loss (at least 10%) was associated with greater improvement.

Discussion & Conclusion

Andrew Schrepf, PhD, co-author of the study and research investigator at the university’s Chronic Pain and Fatigue Research Center, noted that the team’s hypothesis was well-supported by animal research exploring the effects of calorie restriction on pain, and that, in people, there have been interesting positive effects6 on mood observed during religious fasts.

There were significant increases in IL-10 after the study intervention but no significant changes in other cytokine levels. The significantly increased ratio of IL-10 to IL-6 and CRP suggested an increase in anti-inflammatory tone subsequent to caloric restriction. Higher levels of IL-6 were associated with higher modified ACR total scores, both at baseline and after the intervention. However, there were no other associations between cytokines and modified ACR scores.5

The chief finding of the study was that a low-calorie diet improved the spatial distribution of pain and somatic symptoms.5 According to Dr. Schrepf, the results may afford another motivational tool for clinicians when discussing the benefits of weight loss with patients. “The benefits for cardiovascular health are of course extremely important, but I think some patients may respond to the possibility of reducing pain and increasing energy as well,” he told Practical Pain Management.

Akiko Okifuji, PhD, professor of anesthesiology at the University of Utah, provided additional commentary on the relationship between obesity and pain, noting that it is still a young science. She pointed out that, while the Michigan study offered preliminary insights into the intersection of obesity and pain management, not all of the participating subjects were chronic pain patients. Many subjects were reported to have symptoms of fibromyalgia, but not all actually met the criteria of the condition, she said. “We would need to be able to replicate these results in a sample of obese patients with diagnosed chronic pain syndromes.”

Pain Reduction, Gender Disparities, and Future Research

According to the Michigan study, patients reported the greatest pain reductions in the lower back and in weight-bearing areas (eg, knees, hips), as well as improvements in the jaw, chest, and abdomen. Both Drs. Schrepf and Okifuji agreed that reduction in jaw pain was an interesting finding, and questioned whether there might be a centralized aspect to it, perhaps related to a decreased generalized sensitization process. Alternatively, the finding might have been related to changes in body mechanics and posture, particularly to the upper back and shoulder areas, which might reduce nearby muscle tension, explained Dr. Okifuji.

The researchers suggested that these results were consistent with changes involving a global neurobiological or psychological mechanism, writing that, “Weight loss may alter patterns of connectivity that is beneficial for the perception of pain.”5 Furthermore, although the researchers reported that 56% of participants increased their activity levels, there was no data to support identifying baseline gender differences in activity levels. While both pain and depression symptoms improved in male and female subjects participating in the weight-loss intervention, there was a large disparity in outcomes for symptom severity between the genders, where men reported substantially greater improvements than women.

Finally, while the study measured changes in the spatial distribution of pain, it did not look at changes in pain intensity. Consequently, the lack of improvement in pain associated with improvement in somatic symptoms most likely reflects the fact that improvements in mood have been associated specifically with reductions in pain intensity and not location, noted the researchers.5

Overall, while long-term effects of the rapid weight-loss program are still to be determined, the initial results are encouraging. “If we can really show that weight loss makes a difference in their pain, that weight loss might facilitate improvement in pain and related problems (such as fatigue, sleep, and depression),” Dr. Okifuji said, “patients might be more willing to commit to weight loss.”

Last updated on: April 2, 2018
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