Monday, January 14, 2013

How Many Calories In?

A very frequent question I receive is, “How many calories should I take in per day?”  Of course the answer varies per person based on many factors.  The general weight loss equation we give to people is calories in must be lower than calories out.  But it IS more complicated than that. 

Our output (calories out) is a result of our metabolism, which is a combination of our Resting Metabolic Rate, EPOC (excess post-exercise oxygen consumption), NEAT (Non-exercise activity thermogenesis), and our calories burned through exercise.  Whew!  That’s a lot!

Our input (calories in) is a little less complicated as it is purely what our diet is composed of.  But then we also have to factor in nutrient timing and macronutrients.

Yikes!  That’s a lot of information!  Where to start?  Let’s start today by calculating our resting metabolic rate; the number of calories your body burns  during the day to keep you functioning.  The most commonly used equation for this is the Mifflin-St. Joer Equation:

RMR= 4.54 x BW in lbs) + (15.875 x HT in inches) – (4.92 x age) -161

RMR=4.54 x BW in lbs) + (15.875 x HT in inches) – (4.92 x age) + 5

So I will use myself as an example.  I weigh 140lbs, am 64 inches tall, and am 32 years old.

Shana’s RMR= (4.54 x 140) + (15.875 x 64) – (4.92 x 32) - 161

Thus my RMR= 1320kcal/day

What do we do with that number?  Remember, in order to lose weight, we must create a caloric deficit.  I tend to shoot for no more than a 500kcal deficit per day. 
Today (Monday) my workout will be a spin class, which is about 500kcal burned.  So my total calories burned today would = 1,820kcal.  To keep that 500kcal deficit I need to keep my caloric intake at 1,320kcal today.   But we also have to take these numbers with a grain of salt.  I know for a fact if I only take in 1,320 calories I will be hungry and low on energy during the day - most likely because of my non-exercise activities and EPOC from previous workouts.  Thus I bump the number up just a bit (to about 1,600kcal) for my own sanity and success.  Listen to your body- don't even feel hungry or full.

Yes the numbers may look scary, but it really is simple math.  Take a few minutes to estimate your resting metabolic rate, multiply is by your activity score, and plan you eating accordingly!


Anonymous Anonymous said...

Sooo, if my RMR is 2081 and I usually exercise between 300 and 500 calories on most days, am I putting myself in starvation mode by eating 1400-1600 calories per day? Psychologically it's hard to bump my calories up by 500 a day from what I'm eating now but I think I might be not consuming enough calories.

1/15/2013 9:19 PM  

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