Definition and Diagnostic Criteria
Sarcopenia is the progressive loss of skeletal muscle mass and strength associated with aging. Diagnosis typically requires evidence of low muscle mass (measured by DXA or bioimpedance) combined with reduced grip strength or slow walking speed. Unlike simple thinness, the concept also covers qualitative changes in muscle such as fat infiltration and fibrosis, so it can develop even when BMI is within the normal range.
Global Prevalence and Age Patterns
Published prevalence estimates vary widely depending on the diagnostic criteria and population studied. Muscle mass tends to decline with age rather than holding steady through adulthood. Ethnic differences in baseline muscle mass mean that universal cutoff values may not apply equally across populations.
What BMI Cannot Detect
The difficult part of sarcopenia is that body weight and BMI alone cannot detect it. When muscle is lost but fat increases, weight stays the same and BMI remains in the normal range. This state is called sarcopenic obesity, and it carries the double burden of declining strength and metabolic disturbance progressing together. Even if the MyRank BMI ranking places you in the normal range, the full picture of your health is not visible without looking at body composition. Reading the qualitative information behind the numbers is what matters.
Prevention Through Resistance Training
Resistance exercise is central to preventing and managing sarcopenia. It is usually combined with adequate protein intake, though the specific targets differ across guidelines and individual circumstances, so checking with a clinician is the safer route. Tracking physical performance metrics over time provides a practical way to monitor whether you are maintaining muscle function relative to your age group.