Fitbit overestimating BMR, can I change it?

[Thuren]

I'm pretty happy with my activity calorie numbers, some people seem to have problems with them but for me they are ok.

However, after a few weeks of basically zero weight loss, I decided to double-check the BMR number fitbit uses. Is it telling me to eat too much?

When I wake up, fitbit tells me I still have 1840 kcal to eat, given my goal of -750kcal/day. My conclusion is that fitbit thinks my BMR is 2590 kcal.

The most accurate formula that doesn't take fat percentage into account is Mifflin and St. Jeors, it tells me my BMR is 1906.

Harris and Benedict gives me the number 2027, so slightly more.

Since fitbit actually measures every single step, my calorie allowance should be the BMR (without the activity level) adjusted for whatever calorie reduction I have. So that's 2590 kcal/day compared to either 1906 kcal/day (or 2027 kcal/day if you use Harris and Benedict.) This would explain why my calorie reduction goal of -750 has given me no weight loss (or increase.)

So clearly, fitbit is overestimating my numbers. Does anyone else have similar problems? Can I change the BMR somehow? The other solution would be to increase my calorie reduction even more, but I'd prefer to get things right to begin with.

[SteveH]

I'm not sure if that's the best way to work out what fitbit thinks your BMR is - it may take into account an assumption of some activity. To check you could look at the calorie burn rate when you are asleep and then multiply that up to get the daily BMR.

I thought that the fitbit calculation of BMR was the same as the Mifflin so I'm surprised if it's that different. Have you checked your profile settings (weight, height, age etc) to make sure they're correct?

Unfortunately, we can't directly adjust the BMR calculation. The nearest we can get to it is to tweak those profile settings but it's a bit of hit and miss until we get the numbers we want.

[Thuren]

My calorie burn rate when I'm asleep is 20 kcal/15 min = 1920 kcal/day, which is very close the the Miffling St Jeor number! You might be right, fitbit might assume I'll be as active as I usually am. I'll make sure this day is as lazy as possible and see what happens with this number 🙂

My profile settings are correct.

[kalimm · Accepted solution]

You should also be able to change the calories that you're allowed so it doesn't assume you'll be active. I'm not sure if you can do it on the app, you'll need to go to Fitbit.com then to your Logs. If you scroll down to your Food Plan, there will be a gear that will say "Change your daily calorie estimate setting" when you hover over it. Sounds like you have the "personalized" option chosen (I think this is the default). Personalized looks at your past activity history and guesses how active you'll be at certain times throughout the day, then adjusts how many calories you're allowed based on that. If you choose Sedentary, then Fitbit will assume you're never active and will not give you extra calories allowed to account for your active times. You could try this out and see if the numbers are closer to what you would expect.

[Thuren]

You were 100% right, I had it set to personalized, and my calorie budget did decrease during the day. Now the calorie calculations make a lot more sense.

They sure are good at hiding settings all over the place though.

Thank you both for helping me out!

[BobSponsler]

Switching it to sedentary helped me too, the estimate looks much more like what a friend calculated my BMR as.  Thanks!

[tickc]

Hi, 

my fitbit way overestimats the calories i can eat. I  can only eat roughly 1300-1400 to maintian my weight if I am doing 4 hours of high intensuty aerobics etc, working fulltime nursing and walking to work. I broke my ankle and was sedintary and gained 7 kg. Now I want to lose it and calculators say I need to eat 750-800 a day to lose weight. It's a sad number I know, but I am only 158 cm tall and trying to get back to 49 - 50 kg. At 55 kg I am overweight (to me not other people I realise). I have rolls and  none of my clothes fit.  My problem is fitbit won't go below 1000 cal. I just don't lose weight at 1000. even though I am now walking for excercise. Can someone fix it for the short people in the world??? 

[MarreFitbit]

Welcome to the Fitbit Community @tickc , hope you're doing great today! I'd recommend taking a look at @SebringDon's post, my expert friend in calories. 

Hope that awesome post helps you! 

[Gouki]

Thank you so much.

 im a fairly active person trying to lose weight and my fitbit thinks i burn 5000 + ckal a day!

i start off with almost 2000 ckal to eat. thank you so much. this worked for me 🙂

 iv just been eating 1750 ckal a day instead of believing this thing.

[Jerry3]

I have the same problem. My Garmin does a fairly accurate job. I like the Fitbit device better but it is so inaccurate that it's not really useful without significant manual adjustments. I think it ignored your profile completely. I am 52, but according to my Fitbit I have a burn rate of someone in their 20s or early 30s. I have not come across any way to adjust the broken system it uses.

[Fao82]

1. I am experiencing the same problem where i do not lose weight at 750 deficit plan on fitbit.

2. Normally I would succesfully lose weight only if i feel quite hungry at the end of the day. 

3. With fitbit plan of 750 deficit, i feel comfortable at the end of the day, not hungry. But i started gaining weight, my love handles filled up on this programme. I was shocked!

3. You accurately pointed out that our weight is assumed by fitbit to be a large proportion of muscle mass instead of fat mass. This results in an overestimate of BMR.

4. What I did today to lower my Inflated BMR value, was to minus my weight by 10kg on the app, the app will read this as a 10kg muscles loss and will input a lower BMR value to match that. This is not accurate but it is better than having my BMR overestimated and making the app pretty much useless for fatlosss.

[CraigR12]

You can increase the deficit the Fitbit imposes. If you're not losing weight at 750, you can increase it to 1000. Fitbit needs to allow you to put in a custom deficit requirement. That is a feature that is needed. Seems they're overconfident in the accuracy of their own algorithms because 1,000 may not be enough for some.

[Alexd07]

How do you change your calories estimation

only walked 400 steps and watch says burnt over 1000 calories

[Alexd07]

What did you do to get accurate calories burnt?

mine says burnt over 1000 and no activity today just few steps

[Alexd07]

How do u change to sedentary?