Metrics like total weight loss and BMI don’t accurately determine your metabolic health. (© suriya – stock.adobe.com)
In a nutshell
• Fat distribution matters more than weight alone. Visceral fat area and proportion affect different aspects of health, with proportion being more strongly linked to cholesterol problems while area correlates more with inflammation and insulin resistance.
• Two people with identical BMI or even the same amount of visceral fat can face completely different health risks depending on how their fat is distributed between visceral and subcutaneous compartments.
• Health interventions might need to be tailored to individual fat distribution patterns, with different strategies for those with high visceral fat area versus those with high visceral fat proportion.
BE’ER SHEVA, Israel — Not all belly fat is created equal. While most of us focus on simply losing weight to improve our health, new research suggests that where your fat is stored, and in what proportion, might be just as important as how much you’re carrying.
A study published in BMC Medicine by researchers from Ben-Gurion University of the Negev and international collaborators has found surprising differences in how visceral fat, the fat that wraps around your internal organs, affects health. These differences depend on whether you measure its absolute area or its proportion relative to other fat stores.
Why Belly Fat Type Matters
For years, doctors have known that visceral fat is more active and potentially harmful than subcutaneous fat, the fat that lies just under your skin. However, this new research offers insights that could change how doctors assess obesity-related health risks.
“For clinicians, dietitians, and researchers, these findings offer a new framework for evaluating weight-loss success—one that considers not just how much fat is lost, but what kind of fat is lost and how it affects metabolic health. As precision nutrition and personalized medicine evolve, these results could pave the way for more effective interventions that help people achieve better long-term health outcomes,” says study author Iris Shai, from Ben-Gurion University of the Negev, in a statement.
The Research Approach
The research team combined data from two 18-month lifestyle intervention trials involving 572 participants. Using MRI technology, they measured different fat compartments in participants’ abdomens, tracking changes before and after lifestyle interventions including diet changes and physical activity.
While both visceral fat area and visceral fat proportion (the percentage of visceral fat relative to total abdominal fat) are linked to poor metabolic health, they reflect different aspects of health risk. Visceral fat proportion was more closely tied to lipid problems like high triglycerides, while visceral fat area was more strongly linked to inflammation markers and insulin resistance.
“Two people with the same BMI can have entirely different metabolic risks based on how their visceral fat is distributed. Our research shows that these differences matter when assessing cardiometabolic health risks,” says co-lead study author Hadar Klein.
Different Fat Patterns, Different Health Risks
Think about two patients with identical amounts of visceral fat. The first patient has this visceral fat alongside lots of subcutaneous fat (low visceral fat proportion), while the second has the same visceral fat area but much less subcutaneous fat (high visceral fat proportion). This research shows they likely face different health challenges despite having identical visceral fat measurements by traditional standards.
After 18 months of intervention, study participants lost about 22.5% of their visceral fat area but only saw a modest 1.3 percentage point decrease in visceral fat proportion.
The study found that losing visceral fat area was strongly linked to improvements in insulin resistance, reduced inflammation markers, and decreased leptin (a hormone involved in hunger regulation). Meanwhile, reductions in visceral fat proportion were more strongly associated with improvements in liver enzymes and blood fat levels.
Personalizing Weight Loss Approaches
“Understanding visceral fat dynamics could lead to more effective strategies. People with a high visceral fat proportion may benefit from different dietary and exercise approaches compared to those with a large absolute visceral fat area, says co-lead study author Hila Zelicha.
Currently, most obesity assessments rely on simple measurements like BMI or waist circumference, which don’t distinguish between different fat types or distributions. These tools often miss individuals who have “normal” BMI but unhealthy fat distribution, sometimes called “normal weight obesity.” More sophisticated measures of fat distribution could offer better insights into health risks and guide more personalized treatment approaches.
Someone primarily struggling with insulin resistance might benefit most from interventions targeting visceral fat area reduction, while someone with cholesterol problems might want to focus on strategies that specifically reduce visceral fat proportion.
Beyond the Scale: New Assessment Tools
The study developed models to help estimate visceral fat area and proportion without expensive MRI scans. These models used accessible clinical measurements like waist circumference, age, triglyceride-to-HDL ratios, and various blood markers, potentially making these assessments more accessible in routine clinical care. Unlike previous assumptions that all visceral fat reduction equally improves health, this research shows that different patterns of fat loss may provide distinct health benefits.
The researchers also discovered that not all fat under the skin behaves the same way. While superficial subcutaneous fat (the fat just beneath the skin) was linked to healthier cholesterol levels, deep subcutaneous fat was associated with insulin resistance, which can raise the risk of diabetes. This is just another layer of complexity to how different types of fat affect health.
BMI and total weight loss have been the standard metrics for assessing health improvements for decades. However, this study shows it’s time to look beyond what the scale reads. Understanding distinct fat distribution patterns, even in people with lower BMI, may allow for more targeted prevention strategies against diabetes, heart disease, and metabolic syndrome.
Paper Summary
Methodology
Researchers pooled data from two 18-month randomized controlled trials (CENTRAL and DIRECT PLUS) conducted at the same workplace in Dimona, Israel, involving 572 participants. The trials tested various dietary approaches (low-fat, Mediterranean, and green-Mediterranean diets) with physical activity interventions. Physical activity intensity was measured using Metabolic Equivalent for Task (MET) units, with higher increases in weekly METs predicting greater losses of both visceral fat area and proportion. Using 3-Tesla MRI technology, researchers measured abdominal fat compartments at baseline and after 18 months, distinguishing between visceral fat, deep subcutaneous fat, and superficial subcutaneous fat. They collected comprehensive health metrics including blood pressure, glycemic profiles, lipid levels, liver enzymes, and inflammatory markers.
Results
Participants lost an average of 2.6 kg and reduced waist circumference by 4.8 cm. They experienced a 22.5% reduction in visceral fat area but only a 1.3 percentage point decrease in visceral fat proportion. Both visceral fat measurements were associated with metabolic syndrome, hypertension, and diabetes, but visceral fat proportion better predicted hypertriglyceridemia. Visceral fat area showed stronger associations with inflammation markers like C-reactive protein. After intervention, reductions in both visceral fat measurements improved triglycerides, HbA1c, liver enzymes, and HDL cholesterol. Only visceral fat area reduction correlated with decreased insulin resistance, leptin, and chemerin levels.
Limitations
The study predominantly involved men (88.5%), limiting conclusions about women. MRI measurements assessed fat area rather than volume, though researchers averaged multiple slices. The focus on abdominal fat excluded total body fat distribution patterns and fat in extremities. While MRI provides precise measurements, it’s expensive and impractical for routine clinical use. The workplace setting may affect generalizability to broader populations.
Discussion and Takeaways
This research reveals that visceral fat area and proportion reflect different aspects of metabolic health. Visceral fat proportion better indicates lipid status, while visceral fat area more strongly reflects inflammation and glycemic state. These distinctions have important clinical implications for personalized weight management approaches. Patients with high visceral fat area might benefit most from interventions targeting insulin resistance, while those with high visceral fat proportion might need strategies focused on improving lipid profiles. The predictive models developed could eventually allow clinicians to assess these nuanced fat measurements without expensive MRI scans, potentially transforming obesity assessment and treatment.
Funding and Disclosures
The research was supported by grants from the German Research Foundation, Israel Ministry of Health, Israel Ministry of Science and Technology, and the California Walnuts Commission. The funding providers had no involvement in study design, data collection, analysis, or publication. No competing interests were declared by the authors.
Publication Information
The study, “Visceral adipose tissue area and proportion provide distinct reflections of cardiometabolic outcomes in weight loss; pooled analysis of MRI-assessed CENTRAL and DIRECT PLUS dietary randomized controlled trials,” was published in BMC Medicine on February 4, 2025. It was conducted by researchers from Ben-Gurion University of the Negev in collaboration with teams from Harvard T.H. Chan School of Public Health, University of Leipzig, Tulane University, and Soroka University Medical Center.
