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Obese patients with psoriatic arthritis (PsA) who followed a short-term, very low-energy diet showed improvements in multiple aspects of disease activity, a prospective study found.
Over a period of 6 months, patients on the restrictive diet (640 kcal/day) lost a median of 18.7 kg (41.2 lbs), which represented 18.6% of their weight, according to Eva Klingberg, MD, PhD, of the University of Gothenburg in Sweden, and colleagues.
And the percentage of patients achieving minimal disease activity rose from 29.3% at baseline to 53.7% at 6 months (P=0.002), the researchers reported online in Arthritis Research & Therapy.
That stringent primary endpoint of minimal disease activity required patients to meet at least five of these criteria:
- Tender joint count of 1 or less
- Swollen joint count of 1 or less
- Body surface area affected by psoriasis of 3% or less
- Patient pain on a visual analog scale of 15 mm or lower
- Patient global disease activity of 20 mm or less
- Health assessment questionnaire (HAQ) score of 0.5 or lower
- No more than one tender enthesis
The researchers noted that although it is well recognized that PsA is associated with obesity, as well as with metabolic syndrome and cardiovascular disease, few interventional studies have assessed the effects of weight loss on disease activity and outcomes. Accordingly, Klingberg and colleagues enrolled 41 patients, two-thirds of whom were women and whose median age was 54; the duration of PsA was 17 years.
Nonsteroidal anti-inflammatory drugs were being used by 66% of the patients, conventional disease-modifying anti-rheumatic drugs by 46%, and tumor necrosis factor (TNF) inhibitors by 37%.
The treatment consisted of four daily portions of powder that could be dissolved and consumed as shakes or soup. Depending on whether baseline body mass index (BMI) was above or below 40, the strict diet was maintained for either 16 or 12 weeks, after which time limited food intake was permitted. Support and medical follow-up were provided by physicians, nurses, and dietitians throughout the study.
All participants had weight loss, and BMI declined from a median of 35.2 to 29.7 (P<0.001). Waist circumference decreased from 116 to 95.5 cm (P<0.001).
Secondary endpoints included the PsA Response Criteria (PsARC), which includes improvements in patient and physician disease activity scores and improvements in tender and swollen joint counts, as well as the American College of Rheumatology (ACR) 20%, 50%, and 70% response criteria.
PsARC was achieved by 46.3% of patients and the ACR 20, 50, and 70 responses by 51.2%, 34.1%, and 7.3% of patients, respectively. "As a comparison, randomized controlled trials of TNF inhibitors in PsA have typically reported ACR20 and 50 responses of 50-60% and 30-40%, respectively, whereas the reported ACR 20 and 50 responses to placebo have been 15-25% and 0-5%," the researchers noted.
Weight loss as a percentage of baseline weight correlated with change in Disease Activity Score in 28 joints (rs = 0.464, P=0.002) and change in the HAQ (rs = 0.376, P=0.015). Moreover, ACR20 responses were significantly more common in patients whose weight loss exceeded the median of 18.6% (71% vs 30%).
Laboratory measures including hemoglobin and C-reactive protein also showed significant declines.
In general, the researchers reported, the treatment was well tolerated, with side effects including obstipation, hair loss, and hypotension during the strict phase. A total of 12% of patients noted a psoriasis flare.
Various mechanisms have been suggested for the relationship between PsA and obesity, including the following:
- Immunological factors such as the ability of white adipose tissue to produce cytokines such as TNFα, interleukin (IL)-1β, IL-6, and IL-23 that have been implicated in PsA pathogenesis
- Biomechanical stress on entheses
- Behavioral factors including lower physical activity
In addition, obesity has been linked with heightened pain sensitivity in inflammatory diseases. "We recommend that weight loss treatment should be considered as complementary to pharmacological treatment in patients with PsA and obesity, since weight loss may improve disease activity, effects of drug treatment, and cardiovascular risk profile," Klingberg and co-authors stated.
"The study supports the hypothesis that obesity is involved in the pathophysiology of PsA," they concluded, adding that the patients will be followed for an additional 2 years to evaluate potential long-term effects.
A limitation of the study, the team said, was the lack of a control group.
The study was supported by the Swedish government, the Health and Medical Care Executive Board of Vastra Gotaland, the Gothenburg Society of Medicine, the Inger Bendix Foundation for Medical Research, the Rune and Ulla Amlovs Foundation for Rheumatology Research, Stiftelsen Psoriasisfonden, and the Swedish Rheumatology Association in collaboration with Roche.
The authors reported having no financial relationships.