📝 Editor's Note · 2026-07-22 (afternoon) · by Dr. Elena Morales

My TDEE calculator was off by 200 calories — the activity multiplier that finally matched my scale

I have been tracking calories with MyFitnessPal since January. My TDEE was set to 2,800 cal per day (Mifflin-St Jeor BMR times 1.55 moderately active). I was eating 2,400 cal per day (400 cal deficit). But my weight was not moving for 6 weeks.

The fix: I switched the activity multiplier to 1.375 (lightly active), which dropped my TDEE to 2,600 cal per day. My actual deficit was 200 cal, not 400. I lost 3 lbs in the next 3 weeks — exactly what the math predicted. Lesson: if your weight is not moving despite a 400 cal deficit, your activity multiplier is probably too high. Drop it one level and re-test for 2 weeks.