3500 calories = 1 pound  has been abused recently.

I see sites and even books tell people their BMR—basal metabolic rate—> how much calories their bodies burn per day(also known as energy expenditure) and then tell them to have a calorie deficit of  500 calories per day to loose 1 pound a week.  The logic being 7 days x 500 calories per day = 3500 calories since   3500 calories = 1 pound.

Not so fast….500 calories subtracted daily from a woman on a 1500/day diet (that is BMR=1500 calories burned per day)  vs a guy on a 3500/day diet results in 1/3 of total intake for the woman being taken away and 1/7 of total intake for the guy.  This is going to have pronounced effects on energy levels and weight loss between the two.  The result being too much of a deficit for the woman resulting in a slower metabolism and energy levels.  For the guy he may not even notice anything being that its only 1/7th of his total.

The better way to do this is percentage (%).  Take off between 10 to 20% of your total calories (BMR) for the day  if you’re trying to lose or add 10 to 20% if you are trying to  gain  then monitor how your body reacts and adjust accordingly