Beyond BMI: Is Abdominal Fat Echogenicity the New Key to Morbid Obesity?
"Research suggests ultrasound imaging of abdominal fat can offer more insight into metabolic risk than traditional measures like BMI and waist circumference, especially for postmenopausal women."
Obesity, characterized by excessive fat accumulation, is a major global health concern. While the amount of fat is clearly important, research is increasingly showing that the characteristics of that fat – its quality – may be just as crucial in determining metabolic health. Different fat depots in the body can have varying effects on metabolic risk, leading scientists to investigate how structural and morphological differences within adipose tissue contribute to health problems.
Traditionally, fat quantity has been the primary focus. However, recent studies indicate that assessing fat quality could provide additional insights. Computed tomography (CT) scans have been used to assess fat quality, but concerns about radiation exposure limit their use for widespread screening. This is where ultrasonography comes in. It’s a safe, accessible, and reproducible method for tissue characterization, making it a promising alternative for evaluating fat tissue.
A new study published in the Journal of Clinical Endocrinology and Metabolism explores whether the echogenicity (the ability to bounce back an echo) of abdominal fat tissue, measured by ultrasound, can serve as a qualitative marker of adiposity and a predictor of cardiovascular risk, particularly in postmenopausal women. The study aims to determine if this method offers additional information beyond standard measures like BMI and waist circumference.
Fat Quality vs. Quantity: What the Study Revealed
Researchers at the Vascular Laboratory, Department of Clinical Therapeutics, Alexandra Hospital, Medical School, National and Kapodistrian University of Athens, Greece, conducted a study involving 244 postmenopausal women. The study focused on the echogenicity of subcutaneous adipose tissue (SAT) and preperitoneal adipose tissue (pPAT) – two types of abdominal fat – and its relationship to subclinical atherosclerosis (early signs of arterial disease). A control group of 20 healthy premenopausal women was also included for comparison.
- Participants: 244 postmenopausal women without diabetes and 20 healthy premenopausal women.
- Assessment of Atherosclerosis: Subclinical atherosclerosis was assessed using intima-media thickness (IMT) and the presence of plaques in the femoral and carotid arteries, measured by high-resolution ultrasonography.
- Fat Echogenicity Measurement: Ultrasound images of SAT and pPAT were acquired, and their echogenicity was evaluated using grayscale mean (GSMn) with specialized software. Higher GSMn values indicate greater echogenicity.
- Key Finding: SAT GSMn, but not pPAT, was higher in postmenopausal women compared to premenopausal women. This indicates a change in the quality of subcutaneous fat after menopause.
- Association with Adiposity: SAT GSMn was independently associated with metabolic markers of adiposity, including body mass index (BMI) and waist circumference (WC). This suggests that the echogenicity of subcutaneous fat is related to overall body fat and abdominal fat distribution.
- Link to Atherosclerosis: SAT GSMn was associated with carotid IMT and the presence/number of atheromatous plaques. Higher SAT GSMn was linked to a greater risk of subclinical atherosclerosis.
- Incremental Value: SAT GSMn provided additional predictive value for detecting subclinical atherosclerosis beyond traditional risk factors, insulin resistance, BMI, and WC. This highlights its potential as a novel marker.
- Progression of Atherosclerosis: Increased baseline SAT GSMn was associated with an increased rate of progression in carotid IMT, suggesting that fat quality may influence the development of arterial disease over time.
The Future of Obesity Screening: Is Ultrasound the Answer?
The study concludes that SAT echogenicity may serve as a qualitative marker of adiposity, providing additional clinical value over BMI and WC in postmenopausal women. This opens the door for further investigation into the utility of ultrasonography-derived fat echogenicity as a screening method for morbid obesity and cardiovascular risk.
While the study focused on postmenopausal women, the findings suggest that fat quality, as assessed by ultrasound, could be a valuable tool for risk assessment in other populations as well. Further research is needed to determine the broader applicability of this technique.
Given the accessibility, safety, and reproducibility of ultrasound, assessing abdominal fat echogenicity may become a valuable addition to current screening practices, helping to identify individuals at risk for obesity-related complications and cardiovascular disease earlier and more effectively.