From the Guidelines
A DEXA scan is highly useful for assessing body composition and fat distribution, providing precise measurements of body fat percentage, lean muscle mass, and bone mineral density throughout the entire body, as supported by the most recent study 1. The scan works by passing two different energy levels of X-rays through the body, which are absorbed differently by various tissues, allowing for detailed analysis of body composition.
Key Benefits of DEXA Scans
- DEXA scans can identify regional fat distribution, distinguishing between visceral fat (around organs) and subcutaneous fat (under the skin), which is important since visceral fat carries greater health risks.
- The procedure is quick (typically 10-20 minutes), involves minimal radiation exposure (less than a standard chest X-ray), and requires little preparation beyond wearing metal-free clothing.
- DEXA provides more accurate and comprehensive body composition data than methods like BMI, skinfold measurements, or bioelectrical impedance, making it valuable for monitoring changes in body composition over time, assessing health risks, and evaluating the effectiveness of diet and exercise interventions.
Clinical Applications
- According to the study 1, DEXA has been used extensively to study bone demineralization and osteoporosis and represents a significant advance in body fat assessment because of its ease of use in clinical settings and greater accuracy and precision for the differentiation of lean and fat tissues than earlier methods.
- The study 1 recommends assessment of bone mineral density by dual-energy X-ray absorptiometry (DXA) for all patients from 8 to 10 years of age, and suggests consideration of assessment of body composition in all patients using methods such as DXA.
Limitations and Considerations
- However, studies suggest that DEXA may underestimate body fat at low body fat percentage and overestimate body fat at higher body fat percentage in both adults and children, as noted in the study 1.
- DEXA cannot differentiate subcutaneous from visceral fat adiposity, which is an important consideration in clinical practice. Overall, the use of DEXA scans for assessing body composition and fat distribution is supported by the most recent and highest quality evidence, and can be a valuable tool in clinical practice for monitoring changes in body composition, assessing health risks, and evaluating the effectiveness of diet and exercise interventions 1.
From the Research
Utility of DEXA Scan for Body Composition and Fat Distribution
- The primary use of DEXA (Dual-Energy X-ray Absorptiometry) scans is to measure bone mineral density (BMD) and assess the risk of osteoporosis 2, 3, 4, 5.
- While DEXA scans are not primarily used for assessing body composition and fat distribution, they can provide information on body fat percentage and fat mass 6.
- A study published in 2023 developed a prediction model for bone mineral content (BMC) and BMD using anthropometric and demographic data, including body fat percentage and fat mass 6.
- However, the main focus of DEXA scans is on assessing BMD and osteoporosis risk, rather than body composition and fat distribution 2, 3, 4, 5.
Key Findings
- DEXA scans are useful for diagnosing osteoporosis and assessing fracture risk 2, 3, 4, 5.
- The scans can provide information on BMD, which is essential for diagnosing osteoporosis and monitoring treatment response 2, 3.
- While DEXA scans can provide some information on body composition, they are not the primary tool for assessing body fat percentage and fat distribution 6.
Limitations and Considerations
- DEXA scans have limitations, such as the need for specialized equipment and trained personnel 2, 3.
- The scans may not be suitable for all populations, such as those with metal implants or certain medical conditions 4.
- Alternative methods, such as anthropometric measurements and demographic data, may be used to predict BMD and osteoporosis risk in resource-limited settings 6.