MetabolismEvidence-basedLesson 8 of 32

BMR, TDEE and why your body adapts

Your maintenance calories are not fixed. They move with your muscle, your activity and your history.

5 min+25 XP

The two numbers

Basal metabolic rate is what you'd burn lying still all day. Total daily energy expenditure multiplies that by an activity factor, from about 1.2 for sedentary to 1.9 for athletes.

Lean mass drives BMR

Muscle is metabolically active tissue. This is why Syndova uses the Katch-McArdle equation with your body scan lean mass instead of generic weight-based formulas — it's far more accurate as your body composition changes.

Adaptive thermogenesis

During prolonged dieting your body reduces spontaneous movement — fidgeting, gesturing, pacing — and slightly lowers hormone-driven burn. This is normal, reversible, and the reason for diet breaks rather than endless deficits.

Key takeaways

TDEE = BMR × activity factor.
More lean mass means a higher resting burn.
Long deficits reduce spontaneous movement — plan maintenance phases.

Check your understanding

1 question · answer to earn XP

1. What does BMR measure?

Evidence & sources

This lesson reflects guidance from recognised health bodies and peer-reviewed research.

For education purposes only — not intended to diagnose, treat or replace medical advice.