How do you know you burned 2500 calories in a given day? How do you know you ate 2000 calories? A typical person wouldn't know exactly, but in theory if he did

How do you know you burned 2500 calories in a given day? How do you know you ate 2000 calories? A typical person wouldn't know exactly, but in theory if he did eat exactly 2500 calories or more and he ate exactly 2000 calories or less every day, over a long period of time, he would lose weight averaging about 1 pound per week. Of course there could be other factors at work, such as the body adapting to eating and exercise patterns to more efficiently store and burn fat, which might slow the weight loss. Another thing that makes it hard to follow the mathematical is equation is that you can't measure calories in or out exactly. So you have to overcompensate. Maybe you'd shoot for 600 calories on the treadmill every day, and aim to eat 1900 calories, just in case you over/underestimate burning or storing rates.