Readjusting Weight : Strava vs Garmin

Losing weight is all about approximations.
Dieting is not.
Approximation of calories eaten, consumed, burned, of weight lost, muscles builds, etc..
Keeping a weight log of calories, sport activities, weight and waist size is critical to readjust time to time, and kills some wrong ideas.

Couple of last months weight log

First, I pretty fast realized I would not reach my weight goals before the marathon. There is two parts of that. I cannot limit the intake too much in a high training period. And I am building muscle, which weight more than fat. However, there is some signs that I have become leaner. Waist size decreased. Overall shape. But this doesn't show in the graph.

obviously something happened early December that skewed my numbers. In fact, I did switch to Strava as a running log.
And use the website as a Calories Burned reference.

Yesterday, I double checked on the Garmin Connect system.
Based on Strava I have burned in the last 6 weeks a deficit of 7000 calories on top of my daily deficit (300), which bring us to a theoretical deficit of 20K calories, i.e. more than 5 pounds.
Well, obviously, something in wrong.

Based on the Garmin Website, I actually built a deficit of Only 1300 Calories.
Now, If you extrapolate a bit, you can imagine that I might not burn anymore 2000 Calories / day at rest, but , let's say, 1900.
Some math, and voila, I would have only build a total deficit of 10K calories, i.e. less than 3 pounds. Add the muscle build from the strenuous activity , and you have a picture way closer from reality.

As a conclusion, I decided to not change any weight goal for now, but to use the Garmin Connect calories calculation / approximation for my needs.

Some references:

https://strava.zendesk.com/entries/20959327-Calorie-Calculation

Calorie calculations for runs require that you enter your weight. Strava will use your weight and the elevation data and distance of your run to estimate calories burned. If you're having trouble getting calories calculated for your Runs, check or reset your elevation correction by following the instructions on Elevation Correction for your Activities. Calories for runs are a function of speed (grade adjusted), weight, and moving time. Multiply these together with a scaling factor, and that's the estimate.

http://www.dcrainmaker.com/2010/11/how-calorie-measurement-works-on-garmin.html

It then combines this data with heart rate information from the ANT+ heart rate strap. Specifically, it evaluates the time between heart beats (beat to beat) to determine estimated MET (Metabolic Equivalent), which in turn is used determine actual work expenditure.

In short, no methods are accurate, but personally, I do believe that calories consumption have to be related to effort and effort is directly related to cardiac activity.
In my case, there is no doubts that Strava is way too generous on the expenditure, I have seen more than 1500 calories difference on a single long run.



Well, If you want to feel good and eat cheesecake, might as well stick with Strava ;)