Overweight and psoriasis

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Overweight and psoriasis and psoriatic arthritisIn this article, I discuss the relationship between overweight and psoriasis and how their combination both worsens psoriasis and increase the risk of a number of serious conditions, including cardiovascular disease, diabetes, liver disease and some forms of cancer.  I also review various lifestyle interventions designed to promote weight loss and improve general health.  

It is well recognized that being overweight is a risk factor for the development of psoriasis and psoriatic arthritis.  There is also evidence to show that being overweight reduces the therapeutic benefit of many of the medications used in treating psoriasis.  In other words, if you are overweight you are more likely to have psoriasis and the medications used in treatment, will be less effective.
 
The question is which comes first - does being overweight lead to psoriasis or does having psoriasis make someone more prone to putting on weight? Interestingly there is evidence both ways.  

For example, in the Nurse’s Health Study, researchers followed 67,300 women over a period of 12-years among whom a total of 809 self-reported as having developed psoriasis.  Results showed that women who gained weight were at a substantially higher risk of developing psoriasis – the more weight gained greater the risk.  Women in the overweight category were 21% more likely to develop psoriasis, but those classified as obese were more than twice as likely to develop the disease1.  Other studies have shown that not only the risk but the severity of psoriasis is associated with weight gain and a recent report also confirmed a strong association between body weight and psoriatic arthritis2,3.   

On the other hand, there are studies showing that people with psoriasis don't exercise or eat as well as they might and also drink alcohol to excess, all factors which could help explain why some people gain weight after a diagnosis of psoriasis4.5.  To make matters worse, many people with psoriasis become depressed and many of the commonly prescribed anti-depressants are associated with weight gain6.  

The best explanation is that the relationship between psoriasis and overweight is bi-directional - obesity predisposes to psoriasis and psoriasis increases the risk for weight gain.  Many studies have shown the association to be strong and consistent - but why?7

What is the link between psoriasis and obesity?  
Psoriasis is a chronic autoimmune disease that inflames areas of skin, causing discomfort, itching, and raised skin lesions.  This underlying inflammation is caused by special molecules called cytokines.  It turns out that fat cells also produce inflammatory molecules – called adipokines – which produce a similar inflammatory response to that found in psoriasis.  Importantly, several of these cytokines are common to both obesity and psoriasis8.  

So it seems that as your weight increases, the degree of inflammation also increases, thereby either making existing psoriasis worse or triggering new disease.  This explains why some studies show the severity of psoriasis to be closely related to the degree of overweight or obesity2.  

It is also important to note that if you are overweight, you are significantly less likely to achieve the full benefit of many of the systemic and biologic drugs used to treat the disease8.  
Inflammation and metabolic syndrome. The problem is that low grade inflammation of the sort we find in obesity and psoriasis, can lead directly to a condition called metabolic syndrome8,9.  

Metabolic syndrome is the medical term used to describe a clustering of risk factors, including a large waist measurement, raised blood fats, high blood pressure (hypertension), an increased tendency to develop blood clots and insulin resistance.  

Several studies have shown a strong association between psoriasis and metabolic syndrome10,11.  A large study involving more than 45,000 subjects in the UK (4,065 of whom had psoriasis) found metabolic syndrome in 32%, 36% and 40% of those with mild, moderate and severe disease respectively10.  

But why does this matter?
It matters because the presence of metabolic syndrome in psoriasis and obesity, greatly increases the risk of heart disease, diabetes, stroke and some types of cancer. In addition, inflammation of the liver, known as non-alcoholic fatty liver disease (NAFLD), may also occur12,13.    

So, to summarize, both psoriasis and obesity are inflammatory conditions which increase the risk of metabolic syndrome and thereby the risk of a variety of health problems, including heart disease, type 2 diabetes, liver disease and some forms of cancer.  

Does losing weight make a difference?  
If being overweight makes psoriasis worse, or triggers the disease in the first place, what impact does losing weight have?  More specifically, does losing weight reduce the risk of developing metabolic syndrome and the associated health problems such as heart disease, diabetes, cancer and liver disease?  

Weight loss and metabolic syndrome
There is ample evidence to show that losing weight has a dramatic impact on all the various factors which make up metabolic syndrome.  Weight loss reduces the chronic inflammation which we know is a key feature of obesity and psoriasis14. This translates into lower blood pressure, improvements in insulin and glucose metabolism, reduced blood fats and reversal of liver inflammation. These metabolic improvements dramatically reduce the risk of heart disease, diabetes and cancer15.   

Weight loss and psoriasis
What about the impact of weight loss on psoriasis and psoriatic arthritis?  Several studies have shown that in overweight individuals with psoriasis, losing weight reduces the severity of the disease.  In a well designed study, a total of 60 overweight individuals with psoriasis were divided into two groups, one receiving a low-calorie diet and the other being allowed to eat normally.  At 16-weeks, the dieting group had lost 15.4kg more than the control group and has also experienced a significantly greater reduction in disease severity16. Interestingly, the same researchers followed both groups in this study for a further 48-week period. They found that the diet group maintained both their weight loss and the marked improvement in the severity of their psoriasis17.   

Of course, losing weight is as much about physical activity as it is about diet, so patients with psoriasis should be encouraged to both reduce their calorie intake and increase their activity levels.  In addition, many patients with psoriasis are taking different medications for their disease.  So a key question is whether diet and exercise can improve psoriasis beyond any benefit that medication alone would confer?   

To answer this, researchers divided 303 study participants with moderate-to-severe plaque psoriasis, into two groups. The dietary intervention group ate three low-calorie meals a day and exercised three times a week, while the control group simply attended one informational session on weight loss and psoriasis at the start of the study.  Every study participant had previously tried a systemic treatment, but failed to achieve clearance after four weeks. They maintained this therapy for the duration of the 20-week trial.

Patients on the diet experienced a significant improvement in their psoriasis, measured by changes in their Psoriasis Area and Severity Index (PASI) score. Their median PASI score was reduced by 48 percent.  In comparison, the median PASI score of the control group was reduced by just 25.5 percent.  This study confirms that lifestyle changes can offer a benefit to psoriasis patients over and above the effect of standard treatments18.   

Studies have also shown dramatic improvements in psoriasis among obese patients undergoing weight loss surgery, especially gastric bypass.  In some cases, surgery may result in complete remission of the disease.  Interestingly, reports suggest that improvement of psoriasis is initiated immediately following surgery – well before any weight loss could have occurred19.

Weight loss and psoriatic arthritis
Weight loss and treatment may also work together to improve disease symptoms in overweight people with psoriatic arthritis.  A study published in June in Annals of the Rheumatic Diseases, found that patients who took a certain kind of biologic medication (TNF-α blockers) while losing weight improved more than patients who just took the medication.

A total of 138 overweight individuals with psoriatic arthritis, were divided into two groups: half (69) were given a low-calorie diet (1500 calories a day) and the other a normal diet.   Patients were evaluated once a month, with a final assessment at the end of the six-month study.  Researchers employed many different methods of measuring disease improvement, such as the number of swollen or tender joints, the degree of pain the patient experienced and the severity of skin symptoms. These measurements were combined to determine which patients achieved Minimal Disease Activity (MDA), which was defined as a successful treatment outcome.

Researchers found that almost 45 percent of the patients who lost between 5-10 percent of their body weight—and almost 60 percent of the patients who lost more than 10 percent—achieved MDA.  Interestingly, some individuals in the non-diet group also lost weight and they too benefited in terms of achieving MDA.  This suggests that it is weight loss, not the specific diet, that matters20.  

Author:
Dr David Ashton MD PhD
Medical and Scientific Adviser PAPAA
November 2016

References

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