Clearly, people with psoriatic disease have a higher prevalence of insulin resistance and metabolic syndrome, and the reasons for this are not entirely understood. Obesity is an independent risk factor for the development of psoriasis, and it is also associated with more severe psoriasis.

We have seen that, if you look at the body surface area (BSA) in a large cross section of patients, their likelihood of having metabolic syndrome increases (ie, the larger the BSA affected by psoriasis, the more likely you are to have metabolic syndrome). And that relationship does not appear to be entirely due to obesity, as reported by my lab. In another study, we found a clear relationship between the percent BSA in psoriasis and the incidence of type 2 diabetes. After adjusting for age, sex, and body mass index (BMI), the rates for developing diabetes increased by 20% for every 10% increase in BSA.

These types of findings suggest that BMI is not the only driver for the increased risk of insulin resistance and metabolic syndrome observed in individuals with psoriasis. There is something about psoriasis disease activity in the skin that seems to be predictive of developing diabetes over time. There are some shared overlapping genetic features of psoriasis and diabetes; however, it is very difficult to know for sure whether it is the psoriasis or the skin activity that is really driving the incident diabetes, or whether there are perhaps other factors related to skin that are at play here.

One thing that we do know with greater certainty is that individuals who are very overweight tend to struggle with getting their psoriasis under control and generally do not respond as well to therapy; when they respond well, they are more likely to lose response over time. Additionally, biologic therapies do not meaningfully improve the markers of insulin resistance relative to placebo. Even when you clear the psoriasis, these patients still have a residual risk of having metabolic problems.

Losing weight is a significant challenge. Having a high BMI is often something that people do not want to talk about. Either the clinician does not want to talk about it and/or they are reluctant to bring it up with the patient, or there may be sensitivities about it from the patient’s perspective. I think that clinicians need to let patients know what their options are for managing obesity. So, for example, in addition to a healthy diet, exercise, and medical therapies, we should be mindful of bariatric surgery as an option for certain individuals who have a BMI of greater than or equal to 40, or are more than 100 pounds overweight or have a BMI of greater than or equal to 35 and one or more obesity-related comorbidities. A Swedish study showed that patients who underwent gastric bypass surgery had a reduced risk of developing psoriasis over time and had an improved prognosis of psoriasis, which are powerful findings.

Ultimately, if patients are able to obtain weight control, either through dietary changes and exercise, some of the medical therapies that are becoming available online, or surgical treatments, it can improve not only their overall health but also their psoriasis and their response to psoriasis therapies.