I agree with Tom that as you lose weight, you will spend less energy per mile running simply because you don't need to do as much work as before (because the weight you have to move is less). However, unless you are hooked up to a machine to measure your oxygen intake and carbon dioxide output when you run, you can't really tell how many calories you are burning when running. Don't trust any numbers you get from a treadmill or heart rate monitor because those are based on standard charts based on average energy expenditure from various studies.

The most likely scenario is that you are probably taking in slightly more calories than before. If you ate just one scoop of ice cream a day more than you used to, that would be about 350 excess calories. After 10 days that would be about one pound more of body weight. The same is true if you ate one more big cookie per day or drank about one 20 ounce soda extra per day than before. Unless you are crazy about portioning (weighing your dinner or counting your potato chips, I actually do count out my potato chips before eating...), it is easy to end up eating just a little more than before, and before you know it you also weigh more.

You can run more, but you can swing the balance more if you are more careful about eating. That doesn't mean you have to be a food nazi and/or weigh all your food, but you can simply make some substitutions that are more nutritious and filling but less calorie dense. Instead of a cookie, choose an apple sometimes. Instead of soda, substitute water now and then.

Another factor is that typically after 30 years old, we start to lose around 1% of our muscle mass per year if you don't try to maintain it. Muscle mass requires calories for maintenance, thus as you lose it, you require less calories. That is partially why it's easier to put on weight as we get older, since we don't need as many calories to maintain our bodies but we usually eat the same amount as always.

On a side note, I disagree with Tom about burning the same number of calories per mile as you become a better runner. As you get more running fit, you will become more economical and burn less calories per mile. If you read Physiology of Sport and Exercise (Wilmore, Costill, and Kenney, Human Kinetics, 2008), on page 111:

http://books.google.com/books?id=zQGKmbg18J8C&printsec=frontcover#PPA111,M1

As people become more skillful at performing an exercise, the energy demands during exercise at a given pace are reduced. In a sense, people become more economical.

However, the difference in the calories burned by running before you were fit and after you became more fit is a much smaller factor than your food intake. At 18 miles per week, if you got so economical that you burned 10 calories less per mile, that is still only 180 calories less than before. That's only 3 Oreo cookies worth of calories less than before. And it would take about 20 days until you added one pound of body weight because of the difference in caloric expenditure!

Thanks for the input and information. I probably have been eating more or, at least, not as vigilant about what I ate when I lost that weight. Also, I've been using a Polar HRM to measure the number of cals I burn per run. Are HRMs generally not reliable or just give you a ballpark figure in measuring cals burned?

Thanks again,

Ken

Stlken37

Sorry for highjacking your post.

Milkbaby and figbash it is wonderful that you guys should stop by and contribute on this page. I have been meaning to respond to this post but I was busy. The information that you both gave is great and I am sure that many viewers here appreciate it. I really miss all the folks like you guys from the old CR days.

Stlken

I would second the arguement about following the reading from a T/mill or your HR monitor. I use to get very high numbers like 3500 calories when I went on a 20+ mile run from my Garmin that would be 1lb in body weight. I knew this was way off because if I came close to eating even half that amount in additionally calories I would gain weight. I think I read that conventional wisdom put it at approximately 100 calories for each mile you run irrespective of speed. However, I am leaning to think that even this number is high based on my personal experience.

For clarification, if you're getting the calorie number from a personal
Polar hrm (not the ones on the machines), I believe those numbers are
based on your recorded weight, heartrate (measure of intensity),
duration, and maybe some other stuff like max hr (you might enter it or
it might be calculated from age-based formula). Distance doesn't play a
role since it doesn't know how far you ran. Intensity definitely does
play a role, since I use it during my xt class where we don't go very
far. I may log the number as a measure of volume combining intensity
and duration, but don't really use it. (it's downloaded automatically)

A general rule of thumb is that a 150-lb person running 1 mi on flat, firm terrain in calm conditions burns about
100 cal/mi. (I've seen a forumula somewhere with several factors in
it.) If you're heavier, you'll burn more. If there's uphill, wind,
snow, whatever to increase your effort, you'll burn more per time
spent. I also think (not sure) if it's colder (say 0F vs 50F),
you may burn more as a result of your resting metabolism being greater
in colder temperatures, which is a function of your time outdoors. I
know resting metabolism is higher in cold temps, but I'm not sure if
there's any additional factor in exercise in cold weather - other than
having more clothes on, friction, snow, etc. Also not sure if the
insulatiing clothes reduce the effect of cold - probably do.

As already mentioned, as you get better at running, your heart rate
probably decreases for the same perceived effort or you go faster. This
may result in fewer calories burned for the same distance, but it might
be minor.

You might want to consider increasing the duration of your runs or
other exercise (either individually or total volume) with the same
intensity. While the % of fat burned is greater at lower intensities,
the total amt of fat burned can be greater at higher efforts, so I'm
not sure running at lower effort is beneficial unless it enables you to
run longer.

(As I wrote this, I couldn't remember whether you indicated you were
indoors or outdoors, so whether you were using a machine hrm on a tm.
This format doesn't allow me to see followup posts.)

PS: An interesting article on energy expenditure during running is here - with field experiments, not just lab: http://www.jssm.org/vol5/n4/29/v5n4-29text.php (sorry, my examples always seem to be trail or longer distances, but that's where my fascination is)

For steeper slopes: http://jap.physiology.org/cgi/content/full/93/3/1039

I haven't been able to re-find the website with the formula using weight, slope, wind, etc.

Also, in case it wasn't obvious in my original comments - the calorie indicators on the hrms are approximations, but I have no idea whether they truly relate to calories burned (doubt it) or whether they're just a composite estimate of volume combining time and intensity.

Message was edited by: AKTrail