Using the DEXA Scan as a Pre-Season Baseline for Active People and Athletes

As an athlete or active person, setting a strong foundation for your health and performance before the season starts is essential.

One of the most insightful tools for this is a DEXA (Dual-Energy X-ray Absorptiometry) scan, which provides precise data on body composition.

Often used to measure bone density, the DEXA scan is equally valuable for evaluating fat mass, lean muscle mass, and visceral fat. Understanding these metrics can give you a competitive edge by helping you tailor your training, recovery, and nutrition to your body’s needs.

A pre-season DEXA scan establishes a baseline, allowing you to track changes in body composition over time and optimize energy availability to enhance performance, reduce the risk of injury, and ensure long-term health.

What is a DEXA Scan?

A DEXA scan is a quick, non-invasive test that uses low-dose X-rays to differentiate between bone, fat, and lean tissue. It provides detailed data on:

• Total body fat percentage

• Regional fat distribution

• Lean muscle mass

• Bone mineral density

• Visceral fat (fat around the organs)

Unlike other body composition tests like skinfold calipers or bioelectrical impedance, the DEXA scan is highly accurate and can pinpoint changes in specific regions of the body, such as the arms, legs, and trunk.

Why is a DEXA Scan Important for Establishing a Baseline?

1. Monitor Progress Over Time

Establishing a pre-season baseline allows you to objectively track how your body composition changes throughout the season. You’ll be able to see the direct impact of your training and nutrition on muscle gain, fat loss, or changes in bone density.

2. Reduce Risk of Injury

Low bone mineral density or excessive visceral fat can increase the risk of injuries and long-term health complications. A DEXA scan helps identify these risk factors early, so you can adjust your regimen to avoid overtraining and optimize recovery.

3. Optimize Performance

Understanding your lean muscle mass can help you create a training program focused on maintaining or building muscle in key areas for your sport. This is particularly important for endurance athletes, weightlifters, and anyone pushing their physical limits.

4. Personalized Nutrition and Recovery

With the DEXA scan results, you can optimize your nutrition strategy by ensuring that your body is getting the appropriate macronutrients to support muscle retention and energy output while reducing fat mass.

5. Measure Energy Availability

Energy availability (EA) refers to the amount of energy left for basic physiological functions after accounting for the energy expended during exercise. It is critical for maintaining health and performance, especially for athletes. A DEXA scan provides key data points to calculate your energy availability.

How to Use DEXA Scan Data to Calculate Energy Availability

Energy availability is calculated by taking into account your caloric intake and energy expenditure relative to your lean body mass (LBM). Here’s how you can use your DEXA scan results to help determine your energy availability:

Step 1: Determine Lean Body Mass (LBM)

The DEXA scan provides a precise measurement of your lean body mass, which includes muscle, organs, and tissues (everything except fat). This is important because energy availability is expressed in relation to your LBM.

Step 2: Calculate Total Energy Intake

Energy intake refers to the total number of calories you consume each day through food and beverages. Keep track of your daily calorie intake by using a nutrition app or food diary.

Step 3: Measure Energy Expenditure

Energy expenditure includes all the calories you burn through:

• Exercise

• Daily activities (non-exercise activity thermogenesis or NEAT)

• Basal metabolic rate (BMR), which is the number of calories your body needs to maintain basic functions like breathing and circulation.

There are various methods to estimate your **exercise energy expenditure**, such as using wearables (like heart rate monitors or fitness trackers), and BMR calculators based on age, gender, and weight. You can also calculate total daily energy expenditure (TDEE) by adding your BMR and exercise calories.

Step 4: Calculate Energy Availability

Use the following formula to determine your energy availability:

Energy Availability (EA) = (Energy Intake - Exercise Energy Expenditure) / Lean Body Mass (kg)

For example:

• Energy Intake: 2500 calories

• Exercise Energy Expenditure: 700 calories

• Lean Body Mass (LBM): 60 kg (from DEXA scan)

Energy Availability (EA) = (2500 - 700) / 60 = 30 kcal/kg of LBM

Optimal energy availability (EA) is generally considered to be above 45 kcal/kg of fat-free mass (FFM) per day for athletes. This value is the threshold needed to maintain normal physiological functions, such as hormonal balance, bone health, immune function, and reproductive health, while also supporting athletic performance and recovery.

Energy availability below 30 kcal/kg of LBM can lead to low energy availability (LEA), which may contribute to relative energy deficiency in sport (RED-S), a condition that impairs performance, recovery, and long-term health.

Why Energy Availability Matters for Athletes

• Maintaining optimal energy availability is essential for:

• Preserving lean muscle mass

• Maintaining bone health and preventing stress fractures

• Optimizing recovery and avoiding fatigue

• Balancing hormones and supporting the immune system

Low energy availability can lead to a range of health problems, including menstrual disturbances in women, decreased bone density, impaired muscle function, and chronic fatigue.

By calculating your energy availability using DEXA scan data, you can ensure that your nutrition and training support your body’s needs, enabling you to perform at your best.

Sources:

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Papageorgiou M, Martin D, Colgan H, Cooper S, Greeves JP, Tang JCY, Fraser WD, Elliott-Sale KJ, Sale C. Bone metabolic responses to low energy availability achieved by diet or exercise in active eumenorrheic women. Bone. 2018 Sep;114:181-188. doi: 10.1016/j.bone.2018.06.016. Epub 2018 Jun 19. PMID: 29933113.

Popp KL, Cooke LM, Bouxsein ML, Hughes JM. Impact of Low Energy Availability on Skeletal Health in Physically Active Adults. Calcif Tissue Int. 2022 May;110(5):605-614. doi: 10.1007/s00223-022-00957-1. Epub 2022 Feb 16. PMID: 35171303.

Tarnowski CA, Wardle SL, O'Leary TJ, Gifford RM, Greeves JP, Wallis GA. Measurement of Energy Intake Using the Principle of Energy Balance Overcomes a Critical Limitation in the Assessment of Energy Availability. Sports Med Open. 2023 Feb 22;9(1):16. doi: 10.1186/s40798-023-00558-8. PMID: 36811697; PMCID: PMC9947205.