How does Fitdigits count calories? This question pops up more often then a Whack-a-Mole from those who care about the balance of calories and is touched on many times by others who are just curious. For example, many question why the calories on a manually entered workout are so different from that on shown on a Treadmill or during a workout where heart rate is used.
Background / Overview
- Everyone is different. Yep – even though we share 99% of the same DNA and makeup, that 1% is a doozy of a difference.
- Everyone changes constantly – the more we seem to stay the same, the more we change. A wise man once said “No man stands in the same river twice”. As your fitness level and health changes, so does the number of calories you burn on a constant basis.
- Women and men burn energy (calories) differently. Sorry girls – you just don’t burn calories as quickly, all other things equal.
- Younger people tend to burn energy (calories) more quickly.
- When tracking caloric intake (with a great app like MyFitnessPal) and true calories burned (with a great app like Fitdigits) you’ll get the most accurate, scientific approach to weight management. The most successful people use this method – check out some of the success stories
Things That Affect Calorie Burn
- Your weight – bigger people burn more calories, all other things equal. It takes more effort to walk an 18 minute mile for a 200lb person than it does for a 150lb person.
- Your Gender (see #3 above).
- Your Age (if you are not using heart rate and have not taken a personal Fitness Assessment).
- Your fitness level. Fit people have fine-tuned their bodies into calorie burning machines, and are just plain better at burning calories.
- What type and the intensity of your workout. This can be represented in a number called a “Metabolic Equivalent Table” (MET) number
This can be more accurate with Heart Rate Monitoring– your heart rate actually is WAY more accurate at determining how hard your system is working than guessing at a number located in a table generated from generic testing.
- Time. How long did you workout?
Show Me The Numbers!
OK. Let’s look at a couple different scenarios.
(Bad) Calorie Calculations by Gym Machine Calculations / Activity trackers
If a machine, like a treadmill, knows nothing about you, they will probably use this formula:
Total Calories Burned = Duration in Minutes x (((MET – a number representing the type and intensity of your workout) x 3.5 x 70)/200).
So for an hour long jog the formula would be
Total Calories Burned = 60 x ((5 x 3.5 x 70)/200) = 367 calories.
The MET is a number they guessed, like 5 (from a range of maybe 3 to 16, based on speed) as a guesstimate of how hard you worked and 70Kg (154lbs) is their guesstimate of how much you weigh.
(Better) The Fitdigits Manual Calorie Calcs
When you have a person’s weight and can measure basic workout intensity either through self-reporting or by looking at speed/pace, you can start to refine the calorie calculations a bit. The formula is:
Total Calories Burned = Duration in Minutes x (((MET – a number representing the type and intensity of your workout) x 3.5 x your weight in kg)/200).
In this scenario, Fitdigits uses a sliding scale of MET values based on the type of activity chosen and the speed/pace of the workout, cross-referenced with the gender, age and estimated fitness level of the individual (or calculated fitness level/VO2 Max, if they have done a Fitness Assessment), applied to the standard MET tables.
It does assume a flat surface, which isn’t always reflective of reality though, but does get much closer to a real caloric burn number.
If there is no speed/pace (due to no GPS), then calorie calculations are done based on the user-specified Intensity, cross-referenced with the users gender, age and fitness level, if it exists.
(BEST) Calorie Calculations Using Heart Rate – Fitdigits with Heart Rate
With heart rate information, we can actually get very close to real, honest caloric burn numbers.The accurate calculation of calories burned by heart rate is optimized for the heart rate to be between 90 bpm and 150 bpm.
The drivers are: Gender, Weight (kg), Height and VO2max (Fitness Level). The VO2max number is an estimate of fitness level based on a persons age and self-reported fitness level, or a calculated, much more accurate number if an Assessment has been completed.
Men: C/min = (-59.3954 + (-36.3781 + 0.271 x age + 0.394 x weight + 0.404 x VO2max + 0.634 x HR))/4.184
Women: C/min = (-59.3954 + (0.274 x age + 0.103 x weight + 0.380 x VO2max + 0.450 x HR)) / 4.184
Note: Exercise burn formulas are built around total caloric output during exercise — which typically includes BMR.
Kilojoules and Calories
Kilojoules are calculated by the readings we get from the power meters. To convert them to Calories, we take the value of the kilojoule to calories formula and include the metabolic efficiency ratio (typically 20-25%). In detail, a Calorie calculated from 1 kilojoule = 1 / 4.184 / .25 = 1.046 Cal of workout
Calories Per Minute (CPM)
Fitdigits also shows caloric information in terms of “CPM” or Calories Per Minute. This can be an interesting way of thinking about your common activities. Which ones burn the most in the least time, realizing that time dedication really does matter. Also, you can calculate how many minutes will it take to burn off that pint of Ben & Jerrys! 🙂
You can add CPM to any Custom Dashboard). Kind of neat to see how your effort affect burn in a more standardized way!
So now you know how we come up with accurate caloric burn data for you. Now what?
The final piece of the equation is MyFitnessPal. MyFitnessPal takes inventory of everything you eat. Enter in your meals using MyFitnessPal’s enormous library of foods, and it will tell you how many calories you ingested. You can also set weight loss goals so that MyFitnessPal will instruct you on how many calories you can eat based on how much you are working out. Set a goal and reach it with Fitdigits and MyFitnessPal!