How reliable are fitness trackers?

slimlady777
slimlady777 Posts: 1 Member
edited December 2024 in Health and Weight Loss
I've been going to the gym 5 days a week as well as lowering my calorie intake, so far it's going well and I'm healthy under my calorie intake each day. Problem is I'm not sure how reliable the fitness tracker is that's synced to my fitness pal. Today for instance I did 15mins brisk walking, an hour of step aerobics and an hour of Pilates apparently burning over 900 calories. This upped my calorie allowance and I ate over 500 calories of my usual intake but was still 400 calories under what I was able to eat today. However I feel so guilty and keep thinking that the calories lost isn't true, has anyone else experienced the same? Thoughts?

Replies

  • Unknown
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  • jlahorn
    jlahorn Posts: 377 Member
    The short answer is that, in general, they are slightly better than nothing, and some are better than others. Dedicated step counters are pretty accurate for step counting; phone apps less so. Wrist-only HRMs are not particularly accurate. Chest strap HRMs are a little better, but that almost doesn't matter. Most people don't exclusively do the kind of steady-state cardio that are the only thing HRMs can reliably measure. For example, Pilates is not steady-state cardio, so if your device measured it accurately, that's pretty much pure luck :)

    With all that said, 900 total may not be too far off for the activities you describe, depending on your height, weight, and the intensity of the activity.

    I like my FitBit Charge HR a lot. I think the data are interesting and I like to watch the trends. I have tested it against my chest-strap HRM and not found very significant differences in their readings, but I know that I am single anecdote in a sea of conflicting data. There is no way I would bet any significant amount of money that it's even +/- 15% of accuracy on any single activity, though.
  • Mavrick_RN
    Mavrick_RN Posts: 439 Member
    I watch my FitbitCharge HR calorie accumulation with fascination and totally ignore the totals with regard to calorie intake. I apparently burn 3500 to 4000 calories a day but by eating closer to the 1800 calories I am allocated by MFP, I lose about 1.5 to 2lbs a week.

    It totally over estimates calorie burn but it's fun to watch.
  • Pawsforme
    Pawsforme Posts: 645 Member
    I've been using a Fitbit Charge HR for ten months and comparing the TDEE it gives me to calories consumed and weight lost -- I find the TDEE it gives to be very accurate. If anything I believe it slightly under-estimates my TDEE.
  • Vegplotter
    Vegplotter Posts: 265 Member
    They are all good at telling you whether you've walked/exercised more or less than yesterday. But I don't think the metabolism is necessarily as simple as that. Some days you eat more, some less. The amount of exercise you take may mean you need a bit more food - but exactly how much? Too many other variables to rely on them too closely.
  • jessiferrrb
    jessiferrrb Posts: 1,758 Member
    ryry62685 wrote: »
    Its totally unreliable. I set an alarm for 5 0'clock on it to do the dishes and when I came home at 5:30 they were still in the sink.

    *removes hrm from amazon cart; curses world*
  • PAV8888
    PAV8888 Posts: 14,336 Member
    edited June 2016
    Accuracy for any single event/activity differs from all day tracking just like the accuracy of a single item you log may not match the overall accuracy of your caloric logging.

    In any case the "accuracy" of your tracker also depends on how accurately you are recording your caloric intake.

    And on the relative percentage of fat and lean mass you are either gaining or losing.

    In any case, trending weight web-sites (and apps) in conjunction with a spreadsheet like the one I link to below are great tools that can help you figure out how closely your food and activity logging correspond to your weight changes.

    Body composition changes are not accounted for.

    https://docs.google.com/spreadsheets/d/1VDmqNpLPu7sbQSochUJNXdp2F7AN15AGgkvS3zLw1GU/edit?usp=sharing

    Hmmm: can't troubleshoot right now; but it looks like if you're not logged in with a Google account it won't give you the option to save a copy for yourself.
  • NorthCascades
    NorthCascades Posts: 10,968 Member
    edited June 2016
    jlahorn wrote: »
    Chest strap HRMs are a little better, but that almost doesn't matter. Most people don't exclusively do the kind of steady-state cardio that are the only thing HRMs can reliably measure.

    This is going to sound pedantic but please bear with me for a minute because there's an actual point.

    Heart rate monitors don't measure calories, they measure your heart rate.

    Some computer that listens to your HRM estimates how many calories you burned, in part from your heart rate. You can wear a chest strap and have it connected to a watch and also to your phone, do some kind of exercise, and get two different calorie guesses. It's not the HRM's fault! The HRM did its job, it measured your heart rate, and passed that info along.

    HRMs aren't really for calories, in an exercise sense, they're for training by heart rate and for recording your body's response to what you put it through. I can run for more than an hour if I keep my HR below 165 bpm, I don't think I can do 10 minutes above that. When I get "into the zone" I sort of tune out the way my body feels, so I keep an eye on my HR and when it gets close to 165 I slow down a little bit. This is why accuracy matters to me when I'm running.
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