Your basal metabolic rate, or BMR, is how many calories your body burns daily to keep you alive.  That is, even if you were to lie in bed all day, your body would still be burning calories as your heart pumps, your lungs breathe, your brain works, your blood flows, etc.  You can consider this your baseline calorie expenditure.

The older you get, the lower your BMR gets, and the heavier you are, the higher your BMR.  This may seem unfair at first (”Hey, fatter people get to burn more calories doing nothing?!”), but logically, it makes sense; It would require more calories to get the hurt pumping or blood flowing in a body that’s heavy with fat.  Besides, would you rather have a high BMR and be fat or have a lower BMR and be trimmer?

Anyhoo, based on several sources who gave me just very slightly different numbers, my average BMR is 1265.  You can calculate yours at Discovery Health.  What this means for me is that if I were an inactive person who laid in bed all day, I would still be burning at least 1265 calories.

But I’m not an inactive person.  I get up and out of bed, brush my teeth, shower, get dress, rush to the train station, run up and down stairs, rush to work, walk around at work, sit, type, talk, laugh, eat.  Even if I didn’t go to the gym, my normal lifestyle means that I burn more than 1265 calories a day.

Calculating my average calories burned based on my normal activity level is harder than finding my BMR.  People have different burn rates for activities, and one’s burn rate varies from activity to activity depending on the individual’s size.  However, after using some calculators online where I put down my average activity level as “moderately active,” I burn about 705 calories in addition to my BMR, so that’s about 1970 calories burned per day without going to the gym (remember, I do a lot of very brisk walking in order to get to and from work and run errands).

So what does this mean?  If I didn’t go to the gym, and maintained my level of normal daily activity, I should not eat more than 1970 calories a day because I will not burn those excess calories.  Excess calories = weight gain.  If I wanted to lose weight, I should eat about 500 calories less per day, so my calorie intake should max out at 1470.

However, I don’t want to lose weight.  I want to lose body fat while building lean muscle mass.  This means I need to increase my activity level (go to the gym) and possibly increase my calorie intake to support the extra calorie expenditure.

Currently, it seems that a gym session for me only burns 190 calories.  I basically only do about 45 minutes of weights.  I need to throw in some cardio or do more intense training.  But let’s keep it at that for now.  So on days when I do go to the gym, my calorie expenditure is:

1265 + 705 + 190 = 2,160 calories

Ugh, I think I eat much more of that per day.  My f irst step will be to calculate, on average, how many calories I eat per day.  I will be using FitDay to keep track of that, starting today, and will post the results after 1 week.

After much research, this Web site summed up the figures I’ve been getting:

“WORKOUT PROGRAM RULE OF THUMB: TARGET A BALLPARK OF 1010-1390 HONEST CALORIES PER DAY if your main goal is fat-loss, and about 1510-2020 calories per day for muscle gain without fat loss. THEORETICAL: estimate your daily burn, then subtract 500 calories daily for every pound of fat you want to lose per week. With energetic daily workouts, you’ll burn about 1890 calories daily (we’re assuming you’re at least moderately active and not totally sedentary the rest of the day). ”

What I don’t like is that it says “musle gain without fat loss.”  I want to gain muscle and lose fat, however, I think that would just go hand in hand.

I think my aim will be to eat about 2,000 calories a day, or about 1,900 on days I don’t go to the gym.  Let’s see what I’ve been doing.

Editor’s note: Don’t ever rely on just one source for figures.  I checked the same calculations over and over at several different Web sites before I was satsified that there was a consensus on the numbers.  Sometimes the results I was given would vary by 5 - 10 calories, so I calculated an average and rounded off to an easy-to-remember number.  It’s important that you check and double-check your sources.  As with all things, diet and exercise especially, opinions differ and methods differ.

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