Excellent point. And this calibrating is a key point as you lose weight--once you drop a significant amount you've got to revise your calorie intake down a comm

Excellent point. And this calibrating is a key point as you lose weight--once you drop a significant amount you've got to revise your calorie intake down a commensurate amount. Estimation is good enough as long as you monitor your progress and tweak it if it's not getting you results.