Body Composition: Why Muscle Mass May Be the Most Important Number You Track

Muscle as a Longevity Biomarker

Skeletal muscle mass is one of the strongest predictors of survival, functional independence, and metabolic health.

Sarcopenia, the age-related loss of muscle mass and function, affects:

• 5–13% of adults aged 60–70

• 10–25% of those aged 70–80

• Up to 50% of adults over 80

Meta-analyses demonstrate sarcopenia is associated with nearly a 1.9-fold increased risk of all-cause mortality.

Muscle loss is not simply part of normal aging. It is a modifiable risk factor.

Understanding Your DEXA Results

Total Lean Mass

Total lean mass includes:

• Skeletal muscle

• Organ tissue

• Connective tissue

• Body water

This means total lean mass alone is an imperfect measure of muscle.

Appendicular Lean Mass Index (ALMI)

ALMI focuses only on lean tissue in the arms and legs.

ALMI = Lean mass of arms + legs ÷ height²

Because the extremities contain predominantly skeletal muscle, ALMI is the most clinically relevant muscle metric.

Cut points for sarcopenia:

• Men: < 7.0 kg/m²

• Women: < 5.5 kg/m²
  

Longevity experts often recommend maintaining ALMI above the 75th percentile.

Consequences of Low Muscle Mass

Sarcopenia increases the risk of:

• Falls and fractures

• Hospitalization

• Disability

• Loss of independence

• Mortality

Low muscle mass and low grip strength together are particularly predictive of adverse outcomes.

Evidence-Based Interventions

1. Protein Optimization

Older adults require more protein than the RDA of 0.8 g/kg/day.

Recommended intake:

• 1.2–2.0 g/kg/day

• 25–30 g per meal

Leucine-rich protein sources are particularly effective in stimulating muscle protein synthesis.

2. Resistance Training

Training 3–4+ times weekly with progressive overload is the most effective strategy to increase or preserve muscle mass.

Even adults in their 70s and 80s can meaningfully increase muscle strength with structured training.

3. Sleep

Sleeping less than 6 hours per night is associated with increased sarcopenia risk and reduced grip strength.

Optimal sleep duration appears to be 6–8 hours nightly.

4. Creatine

When combined with resistance training, creatine supplementation increases lean mass and strength in older adults.

Recommended dose:
5–10 grams daily.

Creatine without exercise provides minimal benefit.

5. Testosterone Optimization

In hypogonadal men, testosterone therapy has been shown to:

• Increase lean mass

• Improve muscle strength

• Preserve muscle during aging

Treatment decisions are individualized and monitored closely.

Emerging Therapies

Bimagrumab

A monoclonal antibody targeting the myostatin pathway.

Clinical trials show:

• 6–8% increase in lean mass

• Fat mass reduction

• Improved body composition when combined with semaglutide

It remains investigational.

Muscle Preservation During GLP-1 Therapy

GLP-1 medications may result in 15–40% of total weight loss coming from lean mass.

To preserve muscle:

• Resistance training 3–4 times weekly

• Adequate protein intake

• Serial DEXA monitoring

  Our Clinical Model

We Combine:

• Objective DEXA data

• ALMI tracking

• Protein optimization

• Structured resistance programming

• Evidence-based pharmacotherapy

• Careful evaluation of emerging therapies

  Muscle mass is one of the most powerful predictors of how well and how long you will live.

  DEXA provides the data to manage it intentionally.

  If you would like to review your DEXA body composition results or develop a muscle optimization plan, contact Paradigm Health.