Tuesday, June 21, 2016

burning calories

Maybe a reader can help me out.

One thing I've never fully understood is how the whole "burning calories" thing works when it comes to exercise. The rule of thumb that I learned (and which you can see here) is that, for every pound you weigh, you burn about 12 calories daily, so to maintain your exact weight, you need to consume [pounds x 12] calories per day. At 270 pounds, then, I need 3240 calories a day just to sustain my weight.* To put it another way: were I to sit around and do nothing all day—including not eating or drinking anything caloric—I'd burn 3240 calories.

My pedometer, when I walk, is measuring calories burned. Yesterday's walk, for example, supposedly burned 2546 calories (I'm really not sure how accurate this count is, but I think it's partly based on the weight I had entered for myself long ago). My question, then, is this: do I add 2546 calories to my BMR-based 3240 calories to get a one-day caloric burn of 5786 calories? Or do I somehow "overlap" the exercise-related burn with my BMR burn to arrive at a lesser figure? I've never understood the math on this.

*We now know this is wildly untrue, at least in my case. As I noted after having done my 14-day experiment, my body's basal metabolic rate is super-slow. I'm sure that I burn far less than 12 calories per pound per day. Were I to actually eat 3200-plus calories a day, I'd likely gain weight faster than Violet Beauregarde inflating into a giant blueberry.



Surprises Aplenty said...

I don't know of specific or average numbers but body fat percentage will play a part. Among other things, your (my) fat is poorly supplied with blood vessels while your muscle is richly supplied with blood vessels. A person with 25% fat and weighing 100kg will need fewer calories than a person of the same weight but 10% fat.

This was the key to how Body For Life (claimed to) worked. In building muscle mass, your resting body would burn more calories so you lose weight even as you rested if you stayed at the same calorie count for food.

Kevin Kim said...


That dovetails with what I've heard. Muscle burns more energy than fat, so becoming more muscular means burning more calories even when at rest, i.e., the addition of muscle increases your BMR.

But do you have insights as to how I'm supposed to count the calories I burn during exercise? Are these burned calories in addition to the calories I'd normally burn when resting? That doesn't seem quite right.

Let's put it this way: imagine that someone burns 3000 calories a day, just by doing nothing. That's 3000 calories over the course of a 24-hour period. Now let's say that that person starts exercising: he power-walks for three hours, and his pedometer says he's burning 1500 calories per walk. Does this mean he's now burning 4500 calories per day (24 hours' normal burn + 3 hours' accelerated burn), or is he burning some lesser amount (21 hours' normal burn + 3 hours' accelerated burn)? I'm going to guess it's the latter, but I'd love confirmation of this.

Charles said...

Don't know if I can really contribute anything of substance hear, but your math in the precious comment seems reasonable. If you think of it in terms of calories burned per hour, it makes sense. So, while sleeping you burn a certain number of calories per hour, while resting you burn a certain number of cph, etc. Then you have strenuous exercise cph, which will be much higher. You add all those up for a given 24-hour period and you have your cpd figure.

That being said, I have no idea how accurate any of the means we use to figure calories burned really are. It is relatively easy to keep track of how many calories we consume (tedious and time-consuming, perhaps, but not hard), but figuring calories burned without medical supervision seems like a semi-educated guess at best.

Charles said...

Oh my god, what was up with me and that first sentence?

precious -> previous
hear -> here


Kevin Kim said...

I thought about saying something, but I knew these were typos.

Surprises Aplenty said...

I have always thought Kevin's comments were ever so precious and was glad others agreed.

I don't vouch for this website but on it you can input exercises and household activities and the time for each. Miscellaneous includes a spot for 'sleep'.

It requires you enter the number of minutes you perform activities but doesn't give a running total or countdown from 1,440 (minutes in a day). It does break down the calories burned per activity, though.
It told me that I burned 700 calories in sleeping for eight and a half hours.