Why does body fat percentage change BMR?
Lean tissue is more metabolically active than fat tissue, so lean mass can make calorie estimates more personalized.
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How BMR and TDEE are calculated
BMR estimates resting energy needs. TDEE multiplies BMR by activity level to estimate daily maintenance calories.
When body fat percentage is known, Katch-McArdle uses lean body mass directly. Otherwise, Mifflin-St Jeor is a strong general-purpose fallback.
Katch-McArdle: BMR = 370 + 21.6 x lean mass (kg) Mifflin-St Jeor men: 10W + 6.25H - 5A + 5 Mifflin-St Jeor women: 10W + 6.25H - 5A - 161
Frequently asked questions
Is TDEE exact?
No. Treat TDEE as a starting point, then adjust after two to three weeks of real weight and intake data.