My health app tells me to eat 500 fewer calories per day in order to lose at least 1 lb. per week. i incorporate cardio into my routine throughout the week, but why is 500 the magic number? the app starts out at 2100 calories. why is 500 significant?

500 fewer calories is just a number, it is a target for you to aim for. Losing weight is an exercise discipline. Whatever energy source you eat during the day and do not burn off with exercise will be stored as fat. So if you eat less and exercise more and you will lose weight. Keep at it but don't make your goal unreasonable. Best wishes

i believe that this rather simplistic formula stems from a very old paper years ago which used the actual fat content in grams in a pound of body fat and the value of 9 calories per gram of fat. The result somehow comes out to needing a reduction in weekly calories of 3500 calories to lose 1 pound in a week. I'm sure I'm confusing you. Maybe someone else in our panel can better explain it.