Methodology

Body Composition vs Weight for Health

Francesco Zen, founder of ZTraining · Last updated 20 June 2026

Why weight alone tells you so little

Two people can weigh exactly the same and be in entirely different positions health-wise, depending on how much of that weight is muscle versus fat. The number on a scale doesn't distinguish between the two.

"Body composition has muscle mass, body fat, and can tell the story about longevity. Weight means nothing."

What actually matters instead

Muscle mass and body fat percentage carry real information about metabolic health, injury resilience, and how someone is likely to age. That's the story worth tracking, not a single number that can mean almost anything depending on what it's made of.

He built Mr Z, an AI coach trained on his methodology to bring the same approach to a wider audience.