Surreal illustration depicting the impact of body fat on blood viscosity and cardiovascular health.

Decoding Your Body: How Overall and Abdominal Fat Impact Blood Viscosity

Beau Callahan in Health & Wellness December 2025 • 4 min read.

"Unraveling the separate mechanisms by which different types of fat affect your health – and what it means for you."

Recent studies have highlighted a concerning link between both general and abdominal obesity and an increased risk of mortality. This has led to a greater emphasis on using measurements like waist circumference and waist-to-hip ratio (WHR) in addition to body mass index (BMI) to assess health risks. However, the question of whether BMI fully accounts for the obesity-related risks, particularly for conditions like diabetes and coronary heart disease (CHD), remains a subject of debate.

To investigate the distinct impacts of overall adiposity (BMI) and abdominal adiposity (WHR) on blood flow properties (rheology), researchers analyzed data from 430 patients. This group represented a wide range of ages (11-77 years) and BMIs (15-50 kg/m²), offering a comprehensive view of how different body compositions affect blood viscosity.

The study aimed to determine how BMI and WHR independently influence blood viscosity, going beyond simply noting correlations. The researchers sought to understand the underlying mechanisms by which different types of fat might impact cardiovascular health. This information can help individuals better understand their own risk factors and take proactive steps toward wellness.

BMI vs. WHR: Unpacking the Separate Effects on Blood Viscosity

Surreal illustration depicting the impact of body fat on blood viscosity and cardiovascular health.

The study confirmed that BMI and WHR are correlated, meaning that higher overall body fat often accompanies higher abdominal fat. Both BMI and WHR were found to be predictors of blood viscosity, suggesting that both overall and abdominal fat contribute to thicker blood.

However, further analysis revealed that the way BMI and WHR affect blood viscosity differs significantly:

BMI's effect on blood viscosity is linked to its correlation with plasma viscosity (the thickness of the liquid portion of blood) and red blood cell (RBC) aggregation (how easily RBCs clump together).
WHR's effect is strongly tied to hematocrit, which is the percentage of red blood cells in the blood. Higher abdominal fat was associated with higher hematocrit, but not with plasma viscosity or RBC aggregation.

Interestingly, when researchers used a statistical method called forward stepwise regression, WHR emerged as a better predictor of blood viscosity than BMI. This suggests that abdominal fat may have a more direct or potent impact on blood thickness than overall fat.

What Does This Mean for You? Key Takeaways

This research underscores the importance of considering both overall body fat and abdominal fat when assessing cardiovascular risk. While BMI provides a general measure of weight, WHR offers a more specific indication of fat distribution, which appears to have a unique influence on blood viscosity.

The finding that abdominal fat is linked to increased hematocrit suggests a possible mechanism by which it raises cardiovascular risk. Higher hematocrit can lead to thicker blood, making it harder for the heart to pump and increasing the likelihood of clots.

Ultimately, these findings support the idea that reducing both overall and abdominal fat is crucial for maintaining healthy blood flow and reducing the risk of heart disease. Focusing on a healthy lifestyle that includes a balanced diet and regular exercise can help manage both BMI and WHR, contributing to improved cardiovascular health.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.3233/ch-2011-1418, Alternate LINK

Title: Both Overall Adiposity And Abdominal Adiposity Increase Blood Viscosity By Separate Mechanisms

Subject: Physiology (medical)

Journal: Clinical Hemorheology and Microcirculation

Publisher: IOS Press

Authors: Jean-Frédéric Brun, Emmanuelle Varlet-Marie, Eric Raynaud De Mauverger, Jacques Mercier

Published: 2011-01-01

Everything You Need To Know

How does overall body fat affect blood viscosity?

Overall adiposity, measured by Body Mass Index (BMI), influences blood viscosity through its effects on plasma viscosity and red blood cell (RBC) aggregation. Plasma viscosity refers to the thickness of the liquid part of the blood, and RBC aggregation describes how easily red blood cells clump together. High BMI can lead to increased plasma viscosity and greater RBC aggregation, both of which contribute to thicker blood. This is significant because thicker blood, also known as increased blood viscosity, makes it harder for the heart to pump blood, potentially increasing the risk of heart disease and other cardiovascular issues.

How does abdominal fat impact blood viscosity?

Abdominal adiposity, measured by Waist-to-Hip Ratio (WHR), primarily affects blood viscosity through its strong association with hematocrit, which is the percentage of red blood cells in the blood. Higher abdominal fat is linked to higher hematocrit levels. The higher the WHR, the greater the percentage of red blood cells, which, in turn, can make blood thicker. This is significant because thicker blood places extra strain on the cardiovascular system. The implications of elevated WHR and its influence on blood viscosity include an increased risk of developing conditions such as coronary heart disease (CHD).

What is blood viscosity and why is it important?

Blood viscosity refers to the thickness and flow characteristics of blood. It's a crucial factor in cardiovascular health. When blood is thicker, it requires more effort for the heart to pump it throughout the body. Increased blood viscosity can lead to elevated blood pressure, increased strain on the heart, and an increased risk of cardiovascular diseases like coronary heart disease (CHD). Understanding and managing blood viscosity is vital for maintaining overall health and reducing the likelihood of heart-related complications.

Why is Waist-to-Hip Ratio (WHR) considered a better predictor of blood viscosity than Body Mass Index (BMI)?

The study revealed that Waist-to-Hip Ratio (WHR) is a better predictor of blood viscosity than Body Mass Index (BMI). This suggests that the distribution of fat, specifically abdominal fat, might have a more direct or potent impact on blood thickness than overall body fat. This is because WHR is more closely related to specific physiological mechanisms affecting blood composition. While BMI offers a general measure of body fat, WHR provides a more detailed assessment of where that fat is stored, which has a greater influence on blood viscosity and thus, cardiovascular health.

What is the relationship between Body Mass Index (BMI) and Waist-to-Hip Ratio (WHR) in relation to blood viscosity?

Both Body Mass Index (BMI) and Waist-to-Hip Ratio (WHR) play essential roles in assessing cardiovascular risk. BMI provides a general understanding of overall body fat, while WHR offers a more specific insight into fat distribution, particularly abdominal fat. Both measurements are correlated. However, they affect blood viscosity through different mechanisms. BMI influences blood viscosity via plasma viscosity and red blood cell (RBC) aggregation, whereas WHR's effect is closely related to hematocrit. Assessing both BMI and WHR is crucial because they provide a more comprehensive picture of the factors that can impact blood viscosity and cardiovascular health. Using them in combination helps to identify individuals at higher risk of heart disease and other related conditions.