It's all about the math

I'm not a huge advocator of just doing something just because someone else said it worked for them. I want to know how it worked and why.  This is the very reason I love Jillian Michaels.  I get a lot of awesome info from her site, but this is my favorite so far.

http://www.everydayhealth.com/fitness-specialist/how-much-how-fast.aspx?xid=nl_LosingItWithJillianMichaels_20110131

For the quick version:  Jillian breaks it down into one of the most logical ways I've seen.  It's all about the math.  First, you have to know your BMR (basal metabolic rate) or the amount of calories you burn off just by doing your daily activities.  Here's the calculation:

For Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
For Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )

So, in order to lose weight, you have to burn more calories than you consume.  One pound of weight equals 1.500 calories.  So, if your BMR is 1,600 and you burn, say, an extra 500 calories in a workout, that's 2100 calories.  Based on how quickly you want to lose weight, you cut down your daily calorie intake accordingly.

BUT, here's another cool fact.  So your BMR is 1,600.  If you do 2, 1-hour sessions of cardio a day (morning and night) you burn 500 calories in each workout.  The morning and night workouts can actually speed up your base metabolism to 2,000.  So you've just burned 3000 calories just by adding 1 extra workout.  As a result, you burn 1500 calories a day, resulting in a weight loss of 3.5-4 pounds a week!!

Don't kid yourself.  There's no way I have enough time to workout 2 hours every single day of the week, but I try it as often as I can.  Every little bit helps, especially when you can speed up your BMR by a little!