Abdominal Obesity and Psoriasis: Investigating Novel Measurements Through NHANES Data

Emerging research is shedding new light on the relationship between abdominal obesity and psoriasis, suggesting that where fat is distributed on the body may be just as critical as how much of it exists. While psoriasis—a chronic, immune-mediated skin disease affecting over 60 million people worldwide—is already known to be associated with obesity, this new analysis provides a more detailed look at how abdominal fat specifically correlates with psoriasis risk, using advanced metrics that move beyond traditional measures like BMI.

The study, which analyzed data from nearly 5,000 participants in the U.S. National Health and Nutrition Examination Survey (NHANES), found that higher levels of abdominal fat, as measured by three novel indicators—the conicity index (C-index), android percent fat, and body roundness index (BRI)—were significantly associated with a greater likelihood of having psoriasis. These findings underscore the importance of recognizing abdominal obesity not just as a general health concern, but as a factor potentially intertwined with psoriasis development and its clinical management.

Researchers used univariate and multivariable weighted logistic regression analyses, along with restricted cubic spline models, to assess these relationships. After adjusting for various confounding factors, including age, sex, race, smoking, alcohol consumption, socioeconomic status, hypertension, and diabetes, the study found that individuals in the highest quartiles of these abdominal fat measures had notably increased odds of psoriasis. Compared to those in the lowest quartile, participants in the top quartile of C-index showed a 148% increased risk, those with the highest android percent fat had a 139% increased risk, and those with the highest BRI faced an 189% higher risk.

Importantly, the research also revealed that this association between abdominal obesity and psoriasis was even more pronounced in people over the age of 40. This is consistent with broader trends showing that abdominal fat tends to accumulate with age, bringing with it metabolic disruptions that could exacerbate or trigger inflammatory diseases like psoriasis.

Although previous studies have already linked general obesity to psoriasis—pointing to shared inflammatory pathways, including the role of adipose tissue in producing pro-inflammatory cytokines such as IL-6 and TNF-α—this new investigation stands out by focusing on abdominal fat specifically. Unlike body mass index, which cannot differentiate between fat and muscle or indicate where fat is concentrated, measures like C-index, android percent fat (obtained via DEXA scans), and BRI are designed to more accurately reflect abdominal and visceral adiposity, which are known to have stronger ties to metabolic and cardiovascular risks.

The study also performed subgroup and interaction analyses, finding that factors such as marital status, income, and alcohol consumption could influence the relationship between abdominal fat and psoriasis. However, no significant non-linear relationships were detected in the spline analyses, suggesting a generally consistent increase in psoriasis risk with higher abdominal fat levels.

Despite its strengths—including a large, nationally representative sample and the innovative use of multiple abdominal obesity indicators—the study’s cross-sectional design means it cannot establish a direct causal relationship. In other words, while the findings strongly support an association, they do not prove that abdominal fat directly causes psoriasis. Moreover, because the analysis relied on U.S. data, the applicability of these results to other populations remains to be confirmed.

Nonetheless, these results add weight to the growing body of evidence suggesting that abdominal obesity should be a critical focus in psoriasis prevention and management strategies. They also highlight the need for clinicians to look beyond BMI when assessing risk profiles in psoriasis patients and to consider how targeted weight management efforts might play a role in reducing not just cardiovascular and metabolic complications, but also potentially the burden of psoriasis itself.

As research continues, understanding the precise biological mechanisms linking abdominal fat to skin inflammation—and whether reducing abdominal obesity can directly lower psoriasis risk or severity—will be essential. For now, these findings provide a compelling rationale for healthcare providers to incorporate abdominal obesity assessments into routine care for patients at risk of or living with psoriasis, emphasizing the broader health imperative of maintaining a healthy waistline.