Thoughts on targets and activity trackers

DX2JX2

Hi, all - I just picked up a Garmin activity tracker late last week (Fenix 5). I know that automatic adjustments to calorie targets based on activity tracker seems to be a regular topic on the board and thought it might help to add some of my initial thoughts. I only have experience with this Garmin thus far...other brands/software may be different. Take with a grain of salt as you please.

I've been tracking my calories/exercise/weight loss manually for about three months now and it's interesting to see how the information provided by the Garmin unit matches up with actual experience. Initial findings:

1.) Thus far, the Garmin has overestimated the amount of calories I burn while running. Over the course of 4 runs, active calories as shown on the watch have been higher than my records by between 10%-25%. Differences seem to get larger as the runs get longer. For reference, the numbers that seem to work for running calorie burns in my manual tracking align very well with the traditional body weight X mileage X 0.63 formula.

2.) The Garmin also classifies calories burned by normal walking or step climbing as 'active' calories. Any steps above zero seems to count as an active calorie burn. For example, my watch showed me as having 16,000 steps on Saturday, but 11,000 of those came from my 6 mile morning run. This means, that I only took 5,000 steps for the rest of the day. Per the Garmin, these 5,000 steps burned about 300 'active' calories. Not only do I not think that those steps should be classified as active (it's safe to say that 5,000 steps in a day could be considered on the low side of 'normal'), but the total calories credited is double what it should be based on my logs. Again, my calorie burn for walking in manual tracking seems to align very closely with the traditional body weight X mileage X 0.31 formula.

3.) Total calories burned in a given day were about 10% higher on the Garmin vs. my manual logs/calculations. All of the differences fall out in calories classified as 'active'. This seems to say that the Garmin likely overestimates active calories, both in amounts burned per a given activity and in total 'activities' performed in a given day.

In short, I can say that 1.) it seems that the Garmin activity tracker overestimates calories for activities by anywhere between 10% and 25% and 2.) I can definitely see how using the Garmin can make the line between 'base' and 'additional exercise' calories very fuzzy based on how it counts and displays calories burned in normal walking and step climbing.

What does this all mean? The TL;DR is as follows:

If you really want control and transparency over your calorie targets and will be using a Garmin activity tracker to automatically capture exercise calories in MFP, it probably makes sense to calculate your calorie targets using a 'sedentary' lifestyle. That way, any calorie calculated by the Garmin as 'active' can truly be considered as incremental to your base calorie goal (and thus added to the calories you eat).

That said, even with this practice, it is still a good idea to "factor down" the incremental calories provided by the Garmin by something around 15% to 20% given the device's tendency to overestimate calorie burns related to physical activity and up to 50% for credits received via normal walking.

tinkerbellang83

You really need to give the tracker about 4 weeks to adjust to your data before you will get more accurate calorie burns.

I have the Vivoactive HR and when I reviewed the data against my weight loss, found it to be underestimating by about 2% - I use it for walking, running, swimming, yoga, pilates and strength training.

I also have my MFP account set to Lightly Active, with negative adjustments enabled. I don't gain any positive calorie adjustment until after I've reached around 5000 steps.

The most sensible thing to do is pick a percentage of them to eat back and review your data after 4-6 weeks compared with your weight loss and adjust accordingly.

NorthCascades

I used my F5X with a power meter. It can be off (for calories) by as much as 5%, but puts me right in the middle of that range of uncertainty. I find this very acceptable.

Tacklewasher

Be sure to turn on negative adjustments in MFP so your the calories included in your activity level vs. number of non-exercise steps gets adjusted.

I broke my VAHR. Cracked the screen. It works but I can't do anything with it. So I ran out last night and grabbed a new one, wouldn't take a charge at all. Now I have to go back and swap it out.