I have found that keeping accurate records has been helpful to me as far as getting in shape, and staying there. That means using quantifiable metrics to measure how much, how far, and how often. Keeping records has helped me immensely although I am throttling back on how, and what, I keep track of, and especially how I do it.
We are obsessed by calories, but for good reason. They do matter, and you ignore them to your peril. I know I did. Unfortunately I think measuring calories burned, and to a lesser extent calories consumed, can be problematic. So what are we talking about?
What is a calorie?
Most of us know that food has a quality about it that we call calories, but what is it? It is:
The amount of energy, or heat, it takes to raise the temperature of 1 gram of water 1 degree Celsius (1.8 degrees Fahrenheit). One calorie is equal to 4.184 joules, a common unit of energy used in the physical sciences.
Most of us think of calories in relation to food, as in “This can of soda has 200 calories.” It turns out that the calories on a food package are actually kilocalories (1,000 calories = 1 kilocalorie). The word is sometimes capitalized to show the difference, but usually not. A food calorie contains 4,184 joules. A can of soda containing 200 food calories contains 200,000 regular calories, or 200 kilocalories.
… needs calories (energy) to survive, without energy our cells would die, our hearts and lungs would stop, and we would perish. We acquire this energy from food and drink.
If we consume just the number of calories our body needs each day, every day, we will probably enjoy happy and healthy lives. If our calorie consumption is too low or too high, we will eventually experience health complications.
The number of calories foods contain tells us how much potential energy they posses. Below are the calorific values of the three main components of the food we eat:
– 1 gram of carbohydrates contains 4 calories
– 1 gram of protein contains 4 calories
– 1 gram of fat contains 9 calories.
How Many Calories Do We Consume By Exercise?
It is technically possible to measure how many calories we are burning with some precession. Unfortunately it is not yet practical (issues with reliability and validity) since it currently requires laboratory conditions although advances in wearable technology coupled with smart phone technology will probably change that in two to five years. In the meantime what we have are essentially estimates, based on laboratory findings. These estimates use calculations that take into account some combination of age, weight, type of activity (running, walking, bicycling, etc.), intensity, and duration . There are several formulas, and it depends on which formula is being used.
How Are Calories Burned Measured?
Most modern exercise equipment has some kind of calories burned function. GPS watches, smart phone apps, and web sites will also give you an estimate, and remember it is an estimate. Accuracy will vary as we are about to see.
Lately I have been using the MapMyRun app on my iPhone 5 to keep track of time, distance, and calories burned while running. It syncs with MyFitnessPal which I switched to from Livestrong’s MyPlate app (which I think was actually better). Before that I used my Timex Marathon GPS watch for time and distance while ignoring the ridiculously low caloric estimates it provided. Instead I ignored the calories burned number on the GPS watch, and used the calories burned calculator from Runners World (which is specifically for running, and is available online) using the time and distance from the Timex. I stopped that practice after I got the iPhone. But, last week I decided to compare the two methods because I suspected the results from MapMyRun were too high.
For 3.19 miles, at a 10:50 pace here are the results from MapMyRun;
Here are the results from Runnersworld.com for the same workout. I used time and distance from MapMyRun.*
My schoolboy arithmetic indicates a difference of over 18%, or nearly 100 calories. I would say that is a significant difference. Subsequent comparisons showed the same pattern. The MapMyRun app is consistently more optimistic when it comes to how many calories I burned.
Which One Is Right?
I have no idea. I know that the Runners World site does not take into account age or gender. MapMyRun has access to all that information, but I do not know if it uses it. I decided to use the more conservative measure from the Runners World website for two reasons:
1. Tired of lugging around the iPhone. I never found a way to secure it comfortably or usefully other than holding it in my hand. Am I turning into one of those people? I hope note. Also, battery life is problematic, and sometimes it just does strange and wacky things.
2. I wanted to be more conservative and go with the lower estimate.
That means I am back to using my Timex GPX watch in conjunction with the Runners World website.
Are There Other Measurements?
Yes. Some consider measurement of the heart rate over time as the best estimate.The Journal of Sports Sciences provides the following two calculations based based on gender:
Males Calories Burned = [(Age x 0.2017) — (Weight x 0.09036) + (Heart Rate x 0.6309) — 55.0969] x Time / 4.184.
Females Calories Burned = [(Age x 0.074) — (Weight x 0.05741) + (Heart Rate x 0.4472) — 20.4022] x Time / 4.184.
Those calculations would be difficult to do in your head while you are out running or on the elliptical machine. Also, have you ever tried to take your pulse rate manually while running? Of course this method requires a heart rate monitor, and the sophisticated software that comes with them. I am still doing my research. My current understanding is that good ones are expensive, and there can be problems with their accuracy as well.
What to do?
I think we are inclined to underestimate the calories we eat, and overestimate the calories we burn. Because of that, I am comfortable in going with the lower number calculated by the Runners World website. I also know there are ongoing issues with reliability and validity when we measure some things (such as calories burned), but we have more mature technology measuring others (such as distance and time). Probably the best we can do is utilize the tools we have with care, caution, and consistency. More later.
*M y tests show reasonable consistency between MapMyRun, the Timex GPS watch, and my bicycle computer regarding distance and time, but between them the calories burned estimates are inconsistent.