Association of Visceral and Subcutaneous Fat with COVID-19 Severity and Clinical Outcomes in Hospitalized Patients

 

Somayeh Livani¹, Elahe Sadat Alavi¹, Alireza Fatemi^2* and Samira Eshghinia³

Citation: Livani S, Alavi ES, Fatemi A, Eshghinia S. Association of Visceral and Subcutaneous Fat with COVID-19 Severity and Clinical Outcomes in Hospitalized Patients. World J Diabetes Metab. 1(1):1-23.

Received: July 19, 2026 | Published: July 30, 2026

Copyright^© 2026 Genesis Pub by Livani S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0). This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are properly credited.

Abstract

Background: Obesity's connection to COVID-19 severity has prompted an investigation into its impact on the immune system. This study explores the relationship between visceral and subcutaneous fat and disease outcomes in COVID-19 patients.

Methods: The study involved 318 hospitalized COVID-19 patients, including 161 women. Lung CT scans assessed lung involvement and measured visceral and subcutaneous fat levels. The ratio of visceral fat to subcutaneous fat was calculated. Patient files were reviewed for ICU admission and mortality rates. SPSS16 software was used for data analysis.

Results: Age significantly influenced disease outcomes (p=0.001). Men had higher mean visceral fat (117.55 ± 51.56), while women had higher mean subcutaneous fat (175.93 ± 79.79) (p<0.001). The over-50 age group had significantly higher mean visceral fat (p=0.021). Higher mean visceral and subcutaneous fat correlated with longer hospital stays (p<0.05). However, no significant associations were found between fat measures, lung involvement severity, ICU admission, or mortality (p>0.05).

Conclusion: Age was significantly linked to disease severity and mortality in hospitalized COVID-19 patients. Visceral fat correlated with longer hospital stays, but not with lung involvement, ICU admission, or mortality. High lung involvement was associated with greater subcutaneous fat, but not significantly. Subcutaneous fat levels were lower in ICU patients and had lower mortality rates, although not statistically significant.

Keywords

COVID-19; Visceral adipose tissue (VAT); Subcutaneous adipose tissue (SAT); Obesity.

Core tip: This study examines the impact of visceral and subcutaneous fat on disease outcomes in 318 hospitalized COVID-19 patients. It highlights that age is a significant factor influencing disease severity and mortality. While men had higher visceral fat and women had higher subcutaneous fat, higher levels of both types of fat were linked to longer hospital stays. However, no significant associations were found between fat measures and lung involvement severity, ICU admission, or mortality. These findings suggest that age and fat distribution play roles in COVID-19 outcomes, but their impact on critical metrics like ICU admission and mortality is limited.

Introduction

In December 2019, we witnessed the emergence of a new form of the disease caused by the coronavirus called the COVID-19 disease, which has become the pandemic of the century in a short period and has affected almost all the societies of the world. The spread of acute respiratory syndrome of the SARS-CoV-2, which emerged in Wuhan, has rapidly spread throughout China and has become a global health threat [1-4].

Although most patients are either asymptomatic or have only a mild flu-like illness, a significant proportion have severe symptoms. However, the factors leading to the severity of the disease are unclear. Hence, careful investigation of factors associated with severe COVID-19 is needed [5-7]. As the epidemic was moving outside of China, there was a need to confirm the clinical characteristics and lethality of COVID-19 in countries with demographic characteristics [5]. This has led to research efforts around the world to identify those at greatest risk of serious illness and death. Preliminary data refer to older people as well as those with diabetes or cardiovascular including high blood pressure, and respiratory or kidney disease. These problems are often concentrated in certain racial groups (eg, African Americans and Asians), who appear to be more vulnerable to worse outcomes from COVID-19 [8].

Recent studies have identified several risk factors that predispose patients to severe disease. These include age, male gender, diabetes mellitus, high blood pressure, cardiopulmonary diseases, and obesity [2,8-10]. One of the important background factors that several studies emphasized is obesity [8,11,12]. The prevalence of obesity is increasing, especially in developed or developing countries. This issue is especially felt during the COVID-19 pandemic. On the other hand, studies indicate a close relationship between the occurrence of obesity and the severity of cardiometabolic events, the exacerbation of inflammatory processes, and the need to use a ventilator in patients with COVID-19 [7,13].

Obesity is also related to disorders of the body's immune systems, increasing the risk of metabolic disorders such as diabetes and cardiovascular diseases, and therefore, the occurrence of various infectious and inflammatory consequences after contracting COVID-19 in obese patients is much more expected than in non-obese patients [14].

Not all body fat stores are created equal. In fact, the amount and distribution of body fat can have a significant impact on the immune system. Fats carry different cardiovascular and metabolic risks [9,15]. Fats have a high ability to accumulate in skeletal muscles or in the form of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), which is considered an indicator of the occurrence and development of obesity and adiposity. The immune system can also be associated with exacerbation of the disease and increased risk of death in patients with COVID-19 [5,8,10,16,17]. SAT is relatively slow, while VAT is a metabolically more active tissue that secretes inflammatory cytokines [9]. VAT is associated with metabolic syndrome, cardiovascular disorders, and increased susceptibility to infection and sepsis [18]. Hence, analysis of the relationship between fat levels Visceral and severity of infection with COVID-19 is very interesting. VAT and SAT can be rapidly and accurately measured and classified using magnetic resonance imaging or computed tomography (CT) [19]. The objective of this study is to examine the correlation between VAT and SAT fat and the severity and outcome of COVID-19 in hospitalized patients.

Methods and Material

Study design

The study design employed in this research is a cross-sectional descriptive approach. The study population consisted of medical records of individuals aged 18 years and above, who were diagnosed with Covid-19 using established diagnostic criteria such as clinical symptoms, lung CT findings, and a positive polymerase chain reaction (PCR) test for coronavirus. These patients were admitted to the hospital and underwent evaluation for the extent of lung involvement as well as measurements of visceral fat and subcutaneous fat using lung CT scans.

Sample selection

At first, by referring to the file of hospitalized patients, background information including gender and age of the people was collected. Then, by examining the results of lung CT, in addition to determining the percentage of lung involvement, the amounts of visceral fat and subcutaneous fat at the level of the upper pole of the kidney and below the costophrenic angle were determined. According to the criteria approved by radiology, we divided the severity of lung involvement into three categories: less than 50% as weak, between 50-75% as moderate, and above 75% as severe [20].

The method of performing subcutaneous and visceral fat work using the OsiriX system:

In the CT scan images from the OsiriX software, in the range of interest (ROI) menu, select the growing region (2D.3D) option, then select the 2D (two-dimensional) option, and then set the upper and lower thresholds according to the fat density and enter the numbers 50 and 150 respectively.

Then, we selected the desired area including subcutaneous or visceral fat at the level of the upper bridge of the kidney and below the costophrenic level, and we selected 1 point in it, and if it corresponds to the area of subcutaneous and visceral fat, the same area was displayed in green color. Otherwise, we chose another point and checked the area selected by the software to see if it matched or not.

We continued this process until the end of the desired result, in which the density of the areas near the selected point was displayed in green color and the fat area of that area was shown as a number. Also, the ratio of visceral fat to SAT was determined. Then, by reviewing the patients' files, admission to ICU as well as the deaths of the patients were investigated and recorded. Finally, the relationship between the measured indicators and disease outcomes was investigated.

Patients who had the criteria for admission to ICU included oxygen saturation drop, ventilator dependence, progressive pulmonary involvement, and the need for intensive care.

Exclusion criteria for this study included patients under 18 years old, referral patients who were admitted more than 14 days after the onset of symptoms, patients without available CT scans for assessing lung involvement and measuring VAT and SAT, pregnant individuals, and patients with various malignancies.

Statistical analysis

The collected data were analyzed using the commercial statistical software SPSS-16. Descriptive statistics, such as frequency tables for qualitative variables and mean and standard deviation for quantitative variables were calculated. Additionally, relevant charts were generated to visualize the data. To examine the relationship between variables and disease severity, independent t-tests or ANOVA tests were employed. Furthermore, t-tests were utilized to compare means between different groups.

The study and all experimental protocols were approved by the Professional Ethics Committee of the Golestan University of Medical Sciences with the ethical code of IR.GOUMS.REC.1401.468. The informed consent was also obtained from all patients for the implementation of this project. All methods were carried out by relevant guidelines and regulations.

Results

This retrospective descriptive cross-sectional study included a total of 318 hospitalized Covid-19 patients. The mean age of the patients was 55.82 ± 15.39 and the mean number of days in the hospital was 11 ± 10.027. The demographic characteristics of the patients are provided in (Table 1).

Mean ± Standard deviation	Max	Min	Variables
55.82 ± 15.32	96	18	Age (years)
11.25 ± 10.02	74	1	Duration of hospitalization (days)
143.69 ± 80.46	475	5	Visceral fat
103.23 ± 49.55	294.30	5	Subcutaneous fat
0.893 ± 0.599	4.11	0.01	Visceral to subcutaneous fat ratio

Table 2: Patients’ abundance with Covid-19 hospitalized by gender and age. 

The CT scans of patients with the lowest and highest amounts of VAT and SAT have also been depicted in (Figure 1-4). During the study period, the overall mortality rate was 23.9%. For individuals over 50 years old, the mortality rate was 32.5%, while it was 7.3% for those under 50 years old (Table 3).

Figure 1: The CT scan of the patient showing the highest amount of visceral fat.

Figure 2: The CT scan of the patient showing the lowest amount of visceral fat.

Figure 3: The CT scan of the patient showing the highest amount of subcutaneous fat.

Figure 4: The CT scan of the patient showed the lowest amount of subcutaneous fat.

Number of patients (percentage)	Outcome	Variable
138 (66.03)	Recovery	≤ 50	Age
68 (67.47)	Death
101 (92.66)	Recovery	>50
8 (7.34)	Death

 

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