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A clinical trial based in Denmark found that obese patients with psoriasis who lost weight through a low-calorie diet experienced a significant improvement in their quality of life, compared to obese psoriasis patients who didn't lose weight.
The patients in the weight-loss group reported less stinging and burning, were less likely to be embarrassed by unsightly lesions, and found that their condition affected their everyday life less often, said Dr. Peter Jensen, of the Copenhagen University Hospital Gentofte, and colleagues.
"Our results emphasize the importance of weight loss as part of a multimodal treatment approach to effectively treat both the skin condition and its [related medical] conditions in overweight patients with psoriasis," the researchers said in the study, which was published online May 29 in the journal JAMA Dermatology.
Psoriasis is a chronic inflammatory skin disease that develops when a person's immune system malfunctions and causes skin cells to grow too quickly. The new skin cells form in days rather than weeks and pile up on the skin's surface, causing scaly, painful lesions.
In the randomized clinical trial, 27 patients were assigned to an intervention group that followed a low-calorie diet and 26 patients were assigned to a control group that continued to eat ordinary healthy foods. Researchers tracked psoriasis symptoms and quality of life using two questionnaires.
The patients on a low-calorie diet ended up losing nearly 34 pounds in 16 weeks, and reported improvements in both their psoriasis symptoms and their overall quality of life.
Dermatologists said the study's results are not surprising, but do reinforce the need for overweight or obese people with psoriasis to try to lose weight.
"Obesity is a huge issue for patients with psoriasis," said Dr. Joel Gelfand, an associate professor of dermatology and medical director of the clinical studies unit at the Hospital of the University of Pennsylvania, in Philadelphia. "If you're obese with psoriasis, psoriasis is less likely to get clear."
There are a couple reasons excess weight can exacerbate a person's psoriasis. First, psoriasis is an inflammatory disease, and obesity is a known cause of inflammation, said Dr. Larry Green, chairman of the research committee for the National Psoriasis Foundation.
"Anytime someone is obese, it's going to affect how their body can heal because it's a stress on the body and stress affects inflammation," Green said. "By losing weight, they're going to reduce the burden on their body."
Another possibility is that obesity may cause immune system responses that are very similar to those prompted by psoriasis.
"Obesity is associated with the same elevations of cytokines in the blood that promote psoriasis," Gelfand said. Cytokines are small signaling proteins used to regulate the body's immune response.
On a more mundane level, obesity also causes skin friction as parts of the body rub against each other, another expert said.
"If skin rubs against skin, psoriasis gets worse," said Dr. Jeffrey Weinberg, a dermatologist at Beth Israel Medical Center in New York City. "Friction makes psoriasis get worse."
Gelfand said it's difficult to draw major clinical conclusions from such a small pilot study, adding that the people in the Danish study suffered from mild to moderate psoriasis and therefore were less likely to experience a vast improvement in their symptoms from weight loss.
"Larger studies in a population of patients with more severe skin disease are necessary to determine if these findings are clinically important," he said.
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