# How accurate do you suppose FitBit is?

## Replies

• Posts: 718 Member
Great thread with some fantastic tips. Now, what fitbit to get...haha jumping on OPs post because I think I'd like one too.
• Posts: 153 Member
Pu_239 wrote: »
This is what you do, everyday you put in excel how many calories your fitbit tells you you burned, and you also input the calories you ate. Do this for a month, now you can see how much weight you SHOULD have lost according to fitbit, and how much weight you ACTUALLY lost.

If you expected to lose 6lbs that month and lost 5. It's off about a pound a month. About 115 calories a day. Reduce your calorie goal by 115. Of course there are other factors such as water weight and stuff, but I think this is as close as you're going to get.

That's a great idea! But it involves maths and data collection, something I must force myself to do, rather than run in the other direction

If you go to the Fitbit website on your profile page, your 30 Day Average Burn and 30 Day Average Intake are listed.

Hmmm...just realized the profile page rounds my height up. Weird. I wonder if they do that for the calorie burns or if they use the height that's actually in my settings.

So take:
30 Day Avg Burn - 30 Day Avg Intake = 30 Day Avg Deficit
30 Day Avg Deficit * 30 = Total Deficit for 30 days
Total 30 Day Deficit/3500 = Expected loss

I then compare the expected loss to what I actually lost. If the expected loss is higher than what actually happened, I do a bit more math to see about how much it was off on a daily basis. If it's a small amount (less than 50 a day) then more than likely my logging was off. I will put the blame on my actual logging because I'm not perfect and I do eat places where I sometimes have to take a WAG at the calories. April was the perfect example of that. Good grief. I think I ate at this Asian Buffet every other weekend or something and who knows how many calories I consumed those days.

Agreed. No need for spreadsheets or math beyond dividing by 3500. For the record, if I am as accurate as possible about my intake I find my fitbit amazingly accurate about my burns as evidenced by my weight loss or gain.

• Posts: 7,062 Member
I have a FitBit flex that I use. How accurate do you suppose the calories burned are?

The only way to gauge the accuracy is to trust your Fitbit for several weeks, then reevaluate your progress. I lost the weight & have maintained for ten months—so by definition, my Fitbit burn = TDEE.
• Posts: 9,131 Member
Pu_239 wrote: »
zyxst wrote: »
Depends on the type of Fitbit. I felt my Ultra was spot on and was comfy using the numbers it gave me for my TDEE. I changed to the Zip and I don't feel the TDEE it gives me is accurate because I'd be losing more weight (eating 1800ish and TDEE is 3000, so should lose 2# a week but barely losing 2# a month), but I do believe the step count is correct.

If you're eating 1,800 calories and fitbit says you burn 3,000 calories. You should have lost 10lbs in a month. It's off by 8lbs. it's off by about 935 calories a day.

3000-935 = 2065

Yeah, I figured that out. Having ovaries which give me a lovely 3# water gain every month means I have to lose 5# in order to get a 2# loss. I'm back to the weight I was a month ago because of that stupid hormonal gain. It's just irritating to be doing so much and have not much to show for it. I'd like to think walking 30k steps a day would impact more. I keep reminding myself it's better than sitting on my butt all day.

When the Zip and One were first out, Fitbit had a blog post comparing the calorie burns of the 3 devices (Ultra, Zip, & One). The One and Ultra were fairly comparable, while the Zip was 20% higher with calorie burns. This is from memory as the post has been either deleted or something.
• Posts: 13,456 Member
I find my flex to be fairly accurate, matches up well with MFP once I increased my activity level (averaging more than 12000 steps a day is definitely not sedentary like I had mine set at) and I eat back the calorie adjustments on MFP. It helped me lose weight predictably and has made the transition to maintenance pretty seamless.
• Posts: 7,062 Member
zyxst wrote: »
Having ovaries which give me a lovely 3# water gain every month means I have to lose 5# in order to get a 2# loss. I'm back to the weight I was a month ago because of that stupid hormonal gain. It's just irritating to be doing so much and have not much to show for it.

Weight loss is not linear. Take measurements and progress photos, too.

Have you synced your Fitbit account with Trendweight.com? It's free, and it shows your trend without all the "noise" from water weight.
• Posts: 27,732 Member
I've been maintaining while eating back every Fitbit calorie for about a year now.
• Posts: 9,131 Member
editorgrrl wrote: »
zyxst wrote: »
Having ovaries which give me a lovely 3# water gain every month means I have to lose 5# in order to get a 2# loss. I'm back to the weight I was a month ago because of that stupid hormonal gain. It's just irritating to be doing so much and have not much to show for it.

Weight loss is not linear. Take measurements and progress photos, too.

Have you synced your Fitbit account with Trendweight.com? It's free, and it shows your trend without all the "noise" from water weight.
Yes, for 3 years. Been keeping photos and measurements for 3.5 years, since I started. I understand about fluctuations, but understanding doesn't make them less annoying. You can look at my Trendweight and know when I'm ovulating.

The bottom pic shows how May is going. Lowest weight on May 8th (155.4) and over the next 12 days, I gained up to 158.8. When my weight was a stable 156.8 for 3 days is my ovulation. If nothing else, I've gotten the good-old Rhythm Method of birth control down pat, lel.

• Posts: 1,083 Member
If it's accurate (relatively speaking) that's even more frustrating for me since I haven't lost any weight. I must be doing something completely wrong and just don't know it. (I did eat cookies yesterday...)

This week it's been:
1388 intake (s/b 1906 per MFP-base calories are 1200) Burn: 2358
1211 intake (s/b 1885) Burn 2337
1392 intake (s/b 1829) Burn 2281
1565 intake (s/b 1585) Burn 2037

That's pretty average for me. My highest calorie burn this month was 2555 and lowest was 1786. Highest calories 1662, lowest 935.

Even if there's about a 20% inaccuracy of logging because I don't have a scale, there is still a deficit, right?
• Posts: 7,062 Member
If it's accurate (relatively speaking) that's even more frustrating for me since I haven't lost any weight. I must be doing something completely wrong and just don't know it. (I did eat cookies yesterday...)

This week it's been:
1388 intake (s/b 1906 per MFP-base calories are 1200) Burn: 2358
1211 intake (s/b 1885) Burn 2337
1392 intake (s/b 1829) Burn 2281
1565 intake (s/b 1585) Burn 2037

That's pretty average for me. My highest calorie burn this month was 2555 and lowest was 1786. Highest calories 1662, lowest 935.

Even if there's about a 20% inaccuracy of logging because I don't have a scale, there is still a deficit, right?

Your diary is private, so there's really no way anyone can answer this for you. You lose weight by eating at a deficit, so logging everything you eat and drink accurately and honestly is the key to success—with or without a Fitbit.

Read the Sexypants post. So much good "how-to" information: http://community.myfitnesspal.com/en/discussion/1080242/a-guide-to-get-you-started-on-your-path-to-sexypants/p1
• Posts: 1,083 Member
editorgrrl wrote: »
If it's accurate (relatively speaking) that's even more frustrating for me since I haven't lost any weight. I must be doing something completely wrong and just don't know it. (I did eat cookies yesterday...)

This week it's been:
1388 intake (s/b 1906 per MFP-base calories are 1200) Burn: 2358
1211 intake (s/b 1885) Burn 2337
1392 intake (s/b 1829) Burn 2281
1565 intake (s/b 1585) Burn 2037

That's pretty average for me. My highest calorie burn this month was 2555 and lowest was 1786. Highest calories 1662, lowest 935.

Even if there's about a 20% inaccuracy of logging because I don't have a scale, there is still a deficit, right?

Your diary is private, so there's really no way anyone can answer this for you. You lose weight by eating at a deficit, so logging everything you eat and drink accurately and honestly is the key to success—with or without a Fitbit.

Read the Sexypants post. So much good "how-to" information: http://community.myfitnesspal.com/en/discussion/1080242/a-guide-to-get-you-started-on-your-path-to-sexypants/p1

I have read that post, thanks. I opened my diary. I don't like it open, too much judgment, but I really would like help.
• Posts: 27,732 Member
editorgrrl wrote: »
If it's accurate (relatively speaking) that's even more frustrating for me since I haven't lost any weight. I must be doing something completely wrong and just don't know it. (I did eat cookies yesterday...)

This week it's been:
1388 intake (s/b 1906 per MFP-base calories are 1200) Burn: 2358
1211 intake (s/b 1885) Burn 2337
1392 intake (s/b 1829) Burn 2281
1565 intake (s/b 1585) Burn 2037

That's pretty average for me. My highest calorie burn this month was 2555 and lowest was 1786. Highest calories 1662, lowest 935.

Even if there's about a 20% inaccuracy of logging because I don't have a scale, there is still a deficit, right?

Your diary is private, so there's really no way anyone can answer this for you. You lose weight by eating at a deficit, so logging everything you eat and drink accurately and honestly is the key to success—with or without a Fitbit.

Read the Sexypants post. So much good "how-to" information: http://community.myfitnesspal.com/en/discussion/1080242/a-guide-to-get-you-started-on-your-path-to-sexypants/p1

I have read that post, thanks. I opened my diary. I don't like it open, too much judgment, but I really would like help.

Couple of questions about your logging. When you have things logged by tbsp or cups, are you using cups/tbsps or are you eyeballing? When you have things logged in grams how are you deciding how much that is since you don't have a scale?

Definitely don't use those "generic- omelet with 3 eggs" entries from the database. Even without a scale you can get more accurate than that. Log 3 eggs. Then log however much milk you used, if any. Then log each vegetable separately. Then whatever kind of oil/butter/etc.
• Posts: 1,418 Member
earlnabby wrote: »
I recently did a test since I wanted to calculate my TDEE using my actual numbers. I added up my calories eaten and added 3500 calories for each pound lost over 30 days. I got a TDEE of 2683 calories. For the fun of it, I took the same 30 days and added up the TDEE calories Fitbit says I burned and got a TDEE of 2776. I would say that coming in with a difference of less than 100 calories is pretty accurate.

The more you wear it, the more accurate it will be. I have had mine for over a year so it has a lot of data to use. I have a flex and wear it 24/7 unless it is charging.

This is helpful. I just purchased a flex and was wondering that same question.
• Posts: 209 Member
My Charge HR is pretty darn accurate. I am losing the weight that is projected based on Fitbit calories burned and daily intake. So that's a good sign!
• Posts: 3,911 Member
It really depends on which type. The Fitbit flex is just an accelerometer/pedometer, so it's estimate of your calorie burn is built off of the mathematical models that take into account your age, weight, height, etc to relate movement activity to calories. There's some "big data" type refinement that Fitbit says they are doing, but I don't know how much more accurate it makes it.

Trackers that also incorporate heart rate or galvanic skin response sensors can also add those datapoints to refine their calorie estimates, and can better track certain activities that accelerometers on the wrist just can't capture. It's still all estimates based on models, however.

These trackers can be valuable tools and help you better achieve your goals, but it's important to understand that the numbers they create have a margin of error, sometimes pretty significant. As long as that error is consistent (like normally 20-25% high or low), you can accommodate it, if it's highly variable it's much less trustworthy.
• Posts: 4,138 Member
I have a One. Overall I've found it very accurate. I'm now in maintenance and I learned that I must eat at/above what it says I burn or I continue to lose weight.
I have a FitBit flex that I use. How accurate do you suppose the calories burned are?

• Posts: 1,083 Member
editorgrrl wrote: »
If it's accurate (relatively speaking) that's even more frustrating for me since I haven't lost any weight. I must be doing something completely wrong and just don't know it. (I did eat cookies yesterday...)

This week it's been:
1388 intake (s/b 1906 per MFP-base calories are 1200) Burn: 2358
1211 intake (s/b 1885) Burn 2337
1392 intake (s/b 1829) Burn 2281
1565 intake (s/b 1585) Burn 2037

That's pretty average for me. My highest calorie burn this month was 2555 and lowest was 1786. Highest calories 1662, lowest 935.

Even if there's about a 20% inaccuracy of logging because I don't have a scale, there is still a deficit, right?

Your diary is private, so there's really no way anyone can answer this for you. You lose weight by eating at a deficit, so logging everything you eat and drink accurately and honestly is the key to success—with or without a Fitbit.

Read the Sexypants post. So much good "how-to" information: http://community.myfitnesspal.com/en/discussion/1080242/a-guide-to-get-you-started-on-your-path-to-sexypants/p1

I have read that post, thanks. I opened my diary. I don't like it open, too much judgment, but I really would like help.

Couple of questions about your logging. When you have things logged by tbsp or cups, are you using cups/tbsps or are you eyeballing? When you have things logged in grams how are you deciding how much that is since you don't have a scale?

Definitely don't use those "generic- omelet with 3 eggs" entries from the database. Even without a scale you can get more accurate than that. Log 3 eggs. Then log however much milk you used, if any. Then log each vegetable separately. Then whatever kind of oil/butter/etc.

Yes, I do measure the food. On occasion, I eyeball it. As far as the omelet, I didn't make it, I bought it at a café. The guy didn't even know if it was 2 eggs or 3.

The grams thing is based on packaging (which I know is inaccurate).
• Posts: 76 Member
Yea I too have a fitbit charge and have really done alot of comparisons to see how accurate and so far I think it's spot on. I even wore a polar chest band for a while with my Charge HR on to compare the calories .. and it was pretty darn close. But I think it's all about how careful you are with how you wear the device too ....

Here is my monthly summary :

fb.jpg 100.4K
• Posts: 243 Member
edited May 2015
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