DEXA body composition
& bone density.

DEXA, also called DXA, stands for dual-energy X-ray absorptiometry.

It uses two very low-dose X-ray beams to distinguish among three major components of the body:

• —Bone mineral
• —Fat tissue
• —Lean soft tissue

Unlike a scale, BMI calculation, or standard body-fat device, DEXA provides regional information—showing not only how much fat and lean mass you have, but where it is distributed.

The scan is noninvasive, painless, and performed while you lie comfortably on an open table.

Your weight alone cannot reveal whether a change came from fat, muscle, water, or bone.

This is especially important when someone is:

• —Losing weight with a GLP-1 medication
• —Beginning hormone or peptide therapy
• —Changing nutrition or exercise habits
• —Trying to gain muscle
• —Recovering from illness, injury, or prolonged inactivity
• —Experiencing menopause, perimenopause, or age-related hormonal changes

A person may lose weight while also losing valuable lean mass. Another person may see little change on the scale while gaining muscle and losing fat.

DEXA helps reveal these changes more clearly.

Bone Loss Is Often Silent

Bones are living tissue. They continually break down and rebuild throughout life, but the balance can shift with aging, hormonal changes, nutritional deficiencies, inactivity, certain medications, and medical conditions.

Low bone density usually causes no symptoms until a fracture occurs.

A DEXA scan can help identify reduced bone mineral density before it becomes visible on a standard X-ray or results in an injury. Bone-density information may help clinicians evaluate for:

• —Osteopenia
• —Osteoporosis
• —Increased fracture risk
• —Changes in bone density over time
• —The effects of aging, menopause, hormone changes, medications, or treatment

Protecting bone density is an essential part of preserving mobility, independence, posture, and physical resilience as we age.

Bone Health Is Not Only an Older-Person Concern

Peak bone mass is generally established earlier in adulthood. What you build—and preserve—during younger years helps create the reserve you carry into later life.

Bone health may be influenced by:

• —Menopause or early menopause
• —Low estrogen or testosterone
• —Low body weight or significant weight loss
• —Inadequate protein, calcium, or vitamin D
• —Sedentary behavior
• —Lack of resistance or weight-bearing exercise
• —Long-term corticosteroid use
• —Certain thyroid, gastrointestinal, autoimmune, or endocrine conditions
• —Smoking or excessive alcohol use
• —A personal or family history of fractures or osteoporosis

Knowing your baseline allows bone health to become part of prevention rather than something addressed only after a fracture.

Not All Body Fat Behaves the Same Way

Visceral fat is stored deep within the abdomen around the internal organs. It is different from the fat located directly beneath the skin.

A person can appear relatively lean—or have a “normal” BMI—and still carry a higher amount of visceral fat.

Higher visceral fat is associated with increased cardiometabolic risk, including:

• —Insulin resistance
• —Type 2 diabetes
• —Abnormal cholesterol and triglycerides
• —Fatty liver disease
• —Chronic inflammation
• —Cardiovascular disease

Understanding visceral fat provides information that body weight, waist size, and appearance alone may not reveal.

DEXA does not directly image every pocket of fat around each organ as a CT or MRI can. Compatible DEXA systems use the abdominal region and validated software to estimate visceral adipose tissue. It is most useful when interpreted with laboratory results, health history, blood pressure, and other clinical findings.

Subcutaneous fat is the fat stored beneath the skin. It makes up much of the fat that can be seen or felt around the abdomen, hips, thighs, and arms.

Although excessive total body fat may still affect health, subcutaneous fat is biologically different from visceral fat and is generally considered less strongly associated with metabolic disease.

Separating these concepts helps answer an important question:

Is abdominal fat primarily stored beneath the skin, or is a meaningful amount concentrated deeper within the abdomen?

This distinction provides more context than body-fat percentage alone.

Lean mass includes muscle and other nonfat soft tissue. Maintaining it is essential for much more than appearance.

Healthy lean mass supports:

• —Strength and physical performance
• —Balance and mobility
• —Glucose regulation
• —Metabolic health
• —Recovery from illness or injury
• —Bone strength
• —Independence with aging

Muscle loss can occur during rapid weight loss, prolonged inactivity, inadequate protein intake, aging, or certain medical conditions.

DEXA can help show whether a health or weight-loss program is reducing fat while preserving lean tissue—one of the most important goals in healthy body-composition change.

DEXA does not provide only one total-body number. It can show how lean mass and fat are distributed across different regions, including the:

• —Arms
• —Legs
• —Trunk
• —Abdominal region
• —Hip and thigh region
• —Right and left sides of the body

This may help identify:

• —Differences between the right and left limbs
• —Areas with relatively lower lean mass
• —Changes following injury or inactivity
• —Whether a fitness program is producing balanced development
• —Where fat loss or lean-mass changes are occurring

DEXA does not test muscle strength or diagnose a specific injury. However, regional results can provide valuable information to guide a more individualized fitness, nutrition, or recovery plan.

DEXA may be valuable for people who:

• —Want a precise baseline for longevity and healthy aging
• —Are beginning a weight-loss or body-recomposition program
• —Use a GLP-1 medication and want to monitor lean-mass preservation
• —Want to gain muscle or improve athletic performance
• —Have lost a significant amount of weight
• —Are entering perimenopause or menopause
• —Have low estrogen, testosterone, or other hormonal changes
• —Have a family history of osteoporosis or fractures
• —Have experienced a fracture, height loss, or prolonged inactivity
• —Take medications that may affect bone health
• —Have concerns about metabolic health or abdominal fat
• —Want to track the effects of nutrition, exercise, hormones, or other clinician-guided therapies
• —Appear lean but want a clearer understanding of internal fat distribution
• —Want information beyond BMI and scale weight

A clinician should determine whether a diagnostic bone-density evaluation is appropriate based on age, history, medications, and individual risk factors.

Depending on the scan performed and the equipment used, your report may include:

Bone Mineral Density

Measures the mineral content and density of specific bones, commonly including the hip and spine during a diagnostic bone-density study.

T-Score

Compares bone density with that of a healthy young adult reference population. T-scores are generally used when evaluating postmenopausal women and adults age 50 and older.

Z-Score

Compares bone density with what is expected for someone of a similar age, sex, and other reference characteristics. This is often more appropriate for younger adults.

Total Body-Fat Percentage

Estimates how much of the body is composed of fat tissue.

Fat Mass

Shows the estimated amount of fat throughout the body and within specific regions.

Lean Mass

Shows nonfat, nonbone soft tissue throughout the body and by region. Although often discussed as “muscle mass,” lean mass is not exactly the same as skeletal muscle.

Visceral Fat Estimate

Estimates fat stored deeper within the abdominal region when supported by the scanner and its software.

Android-to-Gynoid Ratio

Compares fat concentrated around the abdomen with fat around the hips and thighs.

Appendicular Lean Mass

Evaluates lean mass within the arms and legs and may provide useful context when assessing muscle preservation and age-related muscle loss.

One scan provides a baseline. Follow-up scans can reveal the direction in which your health is moving.

Over time, DEXA may help answer:

• —Am I losing fat or muscle?
• —Is my training program increasing lean mass?
• —Is my weight-loss plan preserving muscle?
• —Has my visceral-fat estimate changed?
• —Are both sides of my body developing evenly?
• —Is my bone density stable?
• —Is my current health strategy producing the intended result?

Meaningful changes should be interpreted in context and ideally compared using the same scanner, facility, positioning, and preparation conditions. Hydration, recent exercise, food intake, and other factors can influence body-composition measurements.

The scan is:

• —Noninvasive
• —Painless
• —Performed on an open table
• —Completed without needles or injections
• —Conducted using a very low dose of ionizing radiation

You will be asked to remain still while the scanning arm moves over the body. Clothing or accessories containing metal may need to be removed.

Preparation instructions can vary. For the most useful comparison between body-composition scans, it is helpful to repeat them under similar conditions.

You should tell the imaging team if you:

• —Are pregnant or may be pregnant
• —Recently had imaging involving contrast material
• —Have metal implants or prior orthopedic surgery
• —Take calcium supplements
• —Have had a previous DEXA scan at another facility