Within the last decade, the scope of psoriasis treatment and research has greatly expanded. Over that time, the focal point of much inquiry has been comorbidities. The association between psoriasis and a host of other conditions has been articulated and examined in various studies, the accumulation of which will hopefully point clinicians to a deeper understanding of the relationship between psoriasis and these conditions.

One of the relationships that has long occupied researchers' and clinicians' minds is that of psoriasis and weight. Specifically, many of us still wonder why the average person with psoriasis weighs 200 pounds and the average person with rheumatoid arthritis weighs 160 pounds. We may also ask what can be implied from the Harvard Nurses' Health study that showed a correlation between body mass index and the risk of developing psoriasis.1 In fact, this study revealed that those with a Body Mass Index (BMI) of greater than 35 had a two-fold increased frequency of developing psoriasis, while those with a BMI 30-34.9 had a 63 percent increased frequency of developing psoriasis.

With the available evidence, we can conclude that increased BMI is an independent risk factor for psoriasis in both adult and pediatric patients. The reason for this likely stems from the fact that obesity is an inflammatory disease. While fat is necessary for storage of hormones and equilibrium of glucose metabolism, an increase in adipocytes results in an increase in TNF alpha, which increases the likelihood of psoriasis.

STUDYING THE LINK

Now that the link has been established between obesity and psoriasis, the next logical question is whether weight loss helps in treatment. Case reports have shown that patients who underwent gastric bypass surgery with subsequent weight loss have shown improvement in their psoriasis. In one smaller study, 10 patients with psoriasis undertook a 24-week diet, and by the end of the study 50 percent obtained a Psoriasis Area Severity Index (PASI) of 50 from dieting alone.2

Several larger studies have shown a diminishment of psoriasis in patients who have lost significant amounts of weight. For instance, Naldi, et al. evaluated 303 overweight or obese patients with moderate to severe psoriasis.3 The patients were put into two 20-week cohorts; cohort 1 went on a regimented diet and exercise for 30 minutes three times per week, and those in cohort 2 were given simple informative counseling at baseline about weight loss. At the end of the study, there was a 45 percent improvement in PASI scores in the dietary/exercise cohort compared to a 25 percent improvement in the information- only arm.

Other studies have looked into the effects of diet on the efficacy of certain therapy. A study performed at the Psoriasis Treatment Center of Central New Jersey has shown that weight loss decreases the number of phototherapy sessions needed to clear plaques.4

In another study, authors evaluated 262 patients with average PASI of 20.5 who were started on various biologic agents.5 The dietary group received fewer than 1,000 calories per day for eight weeks. After 24 weeks, the diet group had lost an average of 25 pounds and experienced an 84 percent improvement in PASI, whereas the control group had a 69 percent PASI improvement. Moreover, PASI 75 was achieved in 86 percent of patients in the diet group, as compared to 60 percent in the control group.

In another study, Guida, et al. randomized 44 obese patients treated with immuno-suppressive drugs into two cohorts for six months.6 The first cohort kept to their usual diet, whereas the second cohort was put on a diet relative to their weight (example 165 lb = 70 kg would get 1400 calories per day) enriched with n-3 polyunsaturated fatty acids. Findings indicated a PASI improvement of 70 percent in the first cohort, with DLQI scores decreasing by 14. Those in the second cohort did not show these improvements.

Jensen, et al. found similar results.7 They evaluated 60 obese patients by dividing them into cohorts, the first of which was on a strict 800-1000 daily calorie limit for eight weeks, then increasing to 1,200 calories thereafter, while the patients in the second cohort ate ordinary foods. At week 16, patients in the first cohort lost 32 punds on average and significant PASI improvement. These patients also experienced significant reductions of diastolic blood pressure, resting heart rate, total cholesterol, VLDL cholesterol, triglyceride, plasma glucose, glycated haemoglobin, and tissue plasminogen activator inhibitor.

PROMOTE A HEALTHY LIFESTYLE

With more data indicating the positive benefit of healthy lifestyle on psoriasis, it is important to discuss a broader lifestyle treatment plan with patients when prescribing treatments. It is important to tell patients that exercise and weight loss can improve psoriasis by decreasing inflammatory factors, i.e. alcohol consumption, smoking, and obesity. Although weight loss and healthier living will not clear psoriasis, it seems to be an effective step both in the improvement of psoriasis and decreasing cardiovascular comorbidities associated with the disease. I also instruct patients to visit their primary care doctors for evaluation of cardiovascular disease.

In terms of how to best convey this, I often tell my patients that I will try my best to get them 75 percent or more improved with treatment, but once their psoriasis is better that they have to start taking care of themselves better. This means less alcohol use, smaller portions at dinner, shifting from red meat to fatty fish like salmon, no more smoking, and more exercise. But in regards to an overall message, the most important message to communicate to patients is that proper diet and exercise are hallmarks of effective treatment.

Jerry Bagel, MD, FAAD, is director of the Psoriasis Treatment Center of Central New Jersey.

  1. Setty AR, et al. Obesity, waist circumference and wait changes and risk of psoriasis in women: Nurses Health Study II. Arch Int Med. 8: 2007. 13-27.
  2. Roongpisuthipong W, et al. The effect of weight loss in obese patients with chronic stable plaque-type psoriasis. Dermatol Res Pract. 2013;2013:795932.
  3. Naldi L, et al. Diet and Physical Exercise in Psoriasis. A Randomized Trial. Br J Dermatol. 2013 Nov 14.
  4. Kimball AB, et al. Weight loss in obese patients with psoriasis can be successfully during a course of phototherapy. J Eur Acad Dermatol Venereol. 2012 Dec; 26(12): 1582-1584.
  5. Al-Mutairi N, Nour T. The effect of weight reduction on treatment outcomes in obese patients with psoriasis on biologic therapy: a randomized controlled prospective trial. Expert Opin Biol Ther. 2014 Mar 24.
  6. Guida B, et al. Energy-restricted, n-3 polyunsaturated fatty acids-rich diet improves the clinical response to immunomodulating drugs in obese patients with plaque-type psoriasis: a randomized control clinical trial. Clin Nutr. 2013 Sep 28. pii: S0261-5614(13)00248-3.
  7. Jensen P, et al. Effect of weight loss on the severity of psoriasis: a randomized clinical study. JAMA Dermatol. 2013 Jul;149(7):795-801.