Predicted loss V actual loss
angelsja
Posts: 859 Member
So I got a new fitbit strap on the 30th of April and I crunched the numbers yesterday and according to CICO I should have lost 10.8lbs since the 30th April actual loss 6.6lbs can someone help me with the maths to figure out how far out my fitbit is please so I can adjust?
1
Replies
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10.8lbs - 6.6lbs = 4.2lbs
4.2lbs x 3500cals = 14,700 cals (approx)
14,700 cals / 29 days = 507cals a day
14,700 cals / 30 days = 490cals a day
(Depends on the start / finish days of your sample period.)
Or more simply you are losing approximately 1lb week less than you predicted so roughtly 500 cals / day difference.
The big caveat of course is that weight varies for a lot more reasons than just calorie balance.
If your start and/or end weights were affected by a water weight fluctuation your numbers change a lot.9 -
10.8lbs - 6.6lbs = 4.2lbs
4.2lbs x 3500cals = 14,700 cals (approx)
14,700 cals / 29 days = 507cals a day
14,700 cals / 30 days = 490cals a day
(Depends on the start / finish days of your sample period.)
Or more simply you are losing approximately 1lb week less than you predicted so roughtly 500 cals / day difference.
The big caveat of course is that weight varies for a lot more reasons than just calorie balance.
If your start and/or end weights were affected by a water weight fluctuation your numbers change a lot.
So my fitbit is over estimating by approximately 500 per day
so I need a 1k calories deficit from my fitbit numbers to lose 1lbs a week man that's harsh 0 -
How often do you weigh? If its only once a month then there could be a lot of other factors involved (water retention for various reasons or time of the month, for example) and you might have lost more than you think. If so I'd wait a bit longer for the data to even out over time.
If you weigh daily and look at your weight trend then its a different story but I wouldn't immediately cut 500 cals a day, try reducing it by 250 and see how it goes for a while.
Either way, well done on the 6.6lbs!4 -
10.8lbs - 6.6lbs = 4.2lbs
4.2lbs x 3500cals = 14,700 cals (approx)
14,700 cals / 29 days = 507cals a day
14,700 cals / 30 days = 490cals a day
(Depends on the start / finish days of your sample period.)
Or more simply you are losing approximately 1lb week less than you predicted so roughtly 500 cals / day difference.
The big caveat of course is that weight varies for a lot more reasons than just calorie balance.
If your start and/or end weights were affected by a water weight fluctuation your numbers change a lot.
So my fitbit is over estimating by approximately 500 per day so I need a 1k calories deficit from my fitbit numbers to lose 1lbs a week man that's harsh
There is also the possibility that you may have miscalculated. 1200 is the lowest MFP will give you for weight loss, so don't assume just because you chose 2 lbs you will actually be losing 2 lbs.
If you used actual numbers, and if that's you in the picture, you don't look like you could afford to lose 10 pounds in a month. You may either be doing something wrong with logging food or Fitbit over-estimates your calories by a lot. It does for me when I have the heart rate function active (I had to turn the function off). I don't know why they switched to using heart rate for calculations when some types of activity can ramp up heart rate with little correlation to calorie burn.9 -
10.8lbs - 6.6lbs = 4.2lbs
4.2lbs x 3500cals = 14,700 cals (approx)
14,700 cals / 29 days = 507cals a day
14,700 cals / 30 days = 490cals a day
(Depends on the start / finish days of your sample period.)
Or more simply you are losing approximately 1lb week less than you predicted so roughtly 500 cals / day difference.
The big caveat of course is that weight varies for a lot more reasons than just calorie balance.
If your start and/or end weights were affected by a water weight fluctuation your numbers change a lot.
So my fitbit is over estimating by approximately 500 per day so I need a 1k calories deficit from my fitbit numbers to lose 1lbs a week man that's harsh
It not necessarily a Fitbit problem (or just a Fitbit problem) - there's also the very big factor of the accuracy of food logging, you may be eating more than you believe. It could of course be a bit of both.
Your chosen rate of loss is in your control. It's not as though you aren't already losing at a reasonably fast pace.
If you are happy at your current food intake then not seeing why you wouldn't just carry on and accept your current rate of loss. Aiming for 10lbs a month is only really suitable for people with a lot of weight to lose.
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Excuse me? So a 770+ Cal a day ACTUAL deficit is now not good enough? Haven't we gone down the road of over-resticting before?6
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Yes that's me in the pic but it's old I weigh daily and use a digital food scale for everything using actual numbers 81544 calories burnt from 30/4 - 28/5 43505 calories eaten my problem is if fitbit is over estimating by 500 per day its going to take a 1k calories deficit to lose even 1lb a week 😖0
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Yes that's me in the pic but it's old I weigh daily and use a digital food scale for everything using actual numbers 81544 calories burnt from 30/4 - 28/5 43505 calories eaten my problem is if fitbit is over estimating by 500 per day its going to take a 1k calories deficit to lose even 1lb a week 😖
Alternative view....
You can eat 250cals more than you currently are eating and still lose 1lb a week.
Not really seeing how you can make bad news out of that!10 -
I will also chime in that I believe activity trackers get more accurate over a little bit of time, initially it’s just the algorithm based off the stats you entered, same as MFP but as you use it and it has more data to track it dials in a bit. So if you just got your Fitbit that could be a factor too.1
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You are still losing 1.5 pounds per week! That's a GREAT number!
I know my activity tracker gives me a very "aggressive" calorie burn so I don't quite believe it and do NOT eat back all those calories, but I've had my watch/tracker since August so I've had many months to work out the numbers and figure how how to manage it. No tracker is going to give you a perfectly-right-on-the-money- number, anyway.
Most people would be over the moon losing at your rate. I know its not quite 2 lbs per week but its damn close! Be happy! You could tighten up a bit more or maybe just not eat back 250 less calories from your excercise burn number to get to 2 lbs but you are doing great!7 -
I will also chime in that I believe activity trackers get more accurate over a little bit of time, initially it’s just the algorithm based off the stats you entered, same as MFP but as you use it and it has more data to track it dials in a bit. So if you just got your Fitbit that could be a factor too.
It's not new
I just hadn't used it for awile as the strap broke 0 -
You are still losing 1.5 pounds per week! That's a GREAT number!
I know my activity tracker gives me a very "aggressive" calorie burn so I don't quite believe it and do NOT eat back all those calories, but I've had my watch/tracker since August so I've had many months to work out the numbers and figure how how to manage it. No tracker is going to give you a perfectly-right-on-the-money- number, anyway.
Most people would be over the moon losing at your rate. I know its not quite 2 lbs per week but its damn close! Be happy! You could tighten up a bit more or maybe just not eat back 250 less calories from your excercise burn number to get to 2 lbs but you are doing great!
Thanks I guess I'm just sick of logging I enjoy exercising and I eat pretty well most things fit into my day without even trying I am tempted to try not logging for awhile and see how I get on0 -
Yes that's me in the pic but it's old I weigh daily and use a digital food scale for everything using actual numbers 81544 calories burnt from 30/4 - 28/5 43505 calories eaten my problem is if fitbit is over estimating by 500 per day its going to take a 1k calories deficit to lose even 1lb a week 😖
Device can be reasonable estimate for average consumer - you may not be average in daily or exercise activity.
So distance based and HR-based calorie burn for either is just way off.
Like if you do tons of daily activity steps and the default stride length is used but longer than reality - you could have inflated distance and calorie burn for daily activity.
Your workouts could be totally composed of interval type workouts and almost daily and long - totally inflated calorie burn based on HR-based calculations then.
Your food logging may be totally accurate based on weight - but the nutrition labels being allowed to be upwards of 20% incorrect could always be hitting you in the inflated direction, wiping out some deficit.
If you haven't done stride length confirm and tweak, if your workouts are wrong for HR-based calorie burn - those tweaks could help the situation.
And yet you could still be off by some %. Which is good to know, and good of you to track.
The comment of about water weight differences between start & ending weigh-in can be significant too.
What if you were 2 lbs lower than normal at start because you had been doing low sodium, not even purposely.
What if day before ending weigh-in you had Chinese dinner and hard workout and were 3-4 lbs higher than normal in water weight
How does redoing the math with 5-6 lbs more loss change things in case that happened. I mean, take into account what could have happened and include some figures there too.
Like if you were to include first week of dieting in the math - figures would include extra water weight lost, so the 3500/lb fat loss doesn't apply and skews results.0 -
6.6 lbs lost in a month sounds like great progress most people would be extremely happy with. If I had locked down 6.6 lbs of fat loss in April I'd definitely be rinsing and repeating the exact same food/exercise levels going forward, without any regard for what electronic gadgets are telling me.
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Yes that's me in the pic but it's old I weigh daily and use a digital food scale for everything using actual numbers 81544 calories burnt from 30/4 - 28/5 43505 calories eaten my problem is if fitbit is over estimating by 500 per day its going to take a 1k calories deficit to lose even 1lb a week 😖
So I am counting 29 days. And you said 6.6lbs? So an evidence based weight loss deficit of 797 Cal a day.
Based on the numbers you give, you ate an actual average of 1500 (43505/29), and your evidence based TDEE was 2297 (1500+797).
Your deficit of 797 was 35% of your evidence based TDEE (797/2295*100).
Even for a morbidly obese person this is EXTREMELY aggressive and increases your chances of being impacted long term.
DOUBLE CHECKS FOR YOU TO RUN: Since you're not using a weight trend and you're using scale weight it is play with the numbers time!
What happens if you move your timelines to 27 days (1 in on each side), 25 days, 23 days? What happens if you move your start or end date only? So 28, 27, 26 days moving the start into May and then moving the end date forward to the 25th.
If things don't change too much, then you're looking at fairly valid numbers. If they change a LOT, consider putting your weight into a trend app and then using the TREND as your daily weight for your weight loss (double smoothing if you will).
Also, I would make sure that your starting weight is your weigh in on 30/4 and your ending is on *29*/5, the day after the calories consumed on 28/5 (I've only forgotten to do this with my numbers a few million times). And similarly for all the other time periods you're considering.
You're presenting that your scale and logging validates 66,613 Calories over 29 days, and that your Fitbit estimated a burn of 81,544 Calories.
This is a difference of 14,931 and a % error, expressed as a Fitbit TDEE % error, of 18.31%
All it means is that when you see your "total calories burned today" on MFP after the adjustment... 18% of THE TOTAL CALORIES (not the adjustment) don't exist.
You can use the framework above to "bracket" the number over different days. This number is extremely heavily dependent on the accuracy of your actual food LOGGED logging.
ARE YOU SURE you logged EXACTLY 1500 Calories in EATEN?
Because of the exactness of the number, I am wondering if you're using your TARGET NET Calories here as opposed to using your ACTUAL LOGGED INTAKE. OF COURSE the exactness can be a coincidence. This is a double check, nothing more.
While I am sure that a math or stats person can come up with a function that will figure out how to adjust the above error to tell you what % of the ADJUSTMENT you get from Fitbit you can eat... my simple arithmetic skills don't go that far.
Seriously. I have no idea how to construct a function that would be based on a changing value (the difference between Fitbit TDEE and MFP EXPECTED TDEE), which does increase as your Fitbit TDEE increases, but not at the same rate since the MFP expected TDEE stays constant
The error I know how to calculate (18%) has to do with your TOTAL Fitbit TDEE. If you usually have fairly constant activity days, no problem. But if your activity varies a lot it could be an issue as the size of the 18% as a number will increase the more calories you burn
I know that for myself I just accept that on an very active day I probably want to avoid eating back all the way to my TDEE (leave some of the adjustment on the table) and on less active days leave less of it. On average I know that about 100 to 150 Cal of the TDEE I see on my Fitbit doesn't exist. I don't need to be much more accurate than that as beyond that I would go more with how I feel in terms of actual hunger or what have you.
In any case, BASED ON THE FIGURES YOU HAVE MADE AVAILABLE, approximately 500 Cal of your FITBIT TDEE don't EXIST.
HOWEVER, and this is something you've said a few times, THIS DOESN'T MEAN THAT YOU HAVE TO EAT 1000 or 500 Cal less than you've been to lose at two lbs a week. (and let us not forget that I, at least, most certainly do NOT think you SHOULD be losing at 2lbs a week based on your stats!)
Again, BASED, on YOUR figures as given:
To lose 2lbs a week you would have to eat 1000-770= 230 Cal less a day than you have been, or 1500-230=1,270, which is an EXTREMELY BAD IDEA, in my opinion.
To lose 1.5lbs a week you would have to eat 750-770= -20 Cal less a day, i.e. 20 Cal more than you have been, so 1520 Cal a day as opposed to the current 1500 a day which you've given as your actual calories in.
To lose 1lb a week you would have to eat 500-770= -270 Cal less a day, i.e. 270 Cal more a day than you have been, so 1,770 Calories a day.
The figures are TOTAL CALORIES EATEN (NOT NET). And assume that your output (Fitbit TDEE) remains constant at the apparent level of 2812 Cal a day that it was at during the 29 days in question.
1770 Cal a day for a deficit of 500 with a TDEE of 2270 yields an ALMOST SANE and STILL aggressive 22% deficit off your TDEE and would be a much more recommended solution that would have you losing up to 50lbs during the next 12 months.
Consider that the fastest way to get nowhere is to go so hard that the whole things collapses, only to have to start all over again. And from what I remember, you've already tried fast a few times in the past... just saying.
I would also kindly invite the people who I expect will disagree with my negative view of a larger deficit to explain how, IN THIS INSTANCE, when it is known that excess deficits have led to re-starts, it makes sense to continue to try to get to goal with a more aggressive as opposed to a less aggressive approach.15 -
Yes that's me in the pic but it's old I weigh daily and use a digital food scale for everything using actual numbers 81544 calories burnt from 30/4 - 28/5 43505 calories eaten my problem is if fitbit is over estimating by 500 per day its going to take a 1k calories deficit to lose even 1lb a week 😖
So I am counting 29 days. And you said 6.6lbs? So an evidence based weight loss deficit of 797 Cal a day.
Based on the numbers you give, you ate an actual average of 1500 (43505/29), and your evidence based TDEE was 2297 (1500+797).
Your deficit of 797 was 35% of your evidence based TDEE (797/2295*100).
Even for a morbidly obese person this is EXTREMELY aggressive and increases your chances of being impacted long term.
DOUBLE CHECKS FOR YOU TO RUN: Since you're not using a weight trend and you're using scale weight it is play with the numbers time!
What happens if you move your timelines to 27 days (1 in on each side), 25 days, 23 days? What happens if you move your start or end date only? So 28, 27, 26 days moving the start into May and then moving the end date forward to the 25th.
If things don't change too much, then you're looking at fairly valid numbers. If they change a LOT, consider putting your weight into a trend app and then using the TREND as your daily weight for your weight loss (double smoothing if you will).
Also, I would make sure that your starting weight is your weigh in on 30/4 and your ending is on *29*/5, the day after the calories consumed on 28/5 (I've only forgotten to do this with my numbers a few million times). And similarly for all the other time periods you're considering.
You're presenting that your scale and logging validates 66,613 Calories over 29 days, and that your Fitbit estimated a burn of 81,544 Calories.
This is a difference of 14,931 and a % error, expressed as a Fitbit TDEE % error, of 18.31%
All it means is that when you see your "total calories burned today" on MFP after the adjustment... 18% of THE TOTAL CALORIES (not the adjustment) don't exist.
You can use the framework above to "bracket" the number over different days. This number is extremely heavily dependent on the accuracy of your actual food LOGGED logging.
ARE YOU SURE you logged EXACTLY 1500 Calories in EATEN?
Because of the exactness of the number, I am wondering if you're using your TARGET NET Calories here as opposed to using your ACTUAL LOGGED INTAKE. OF COURSE the exactness can be a coincidence. This is a double check, nothing more.
While I am sure that a math or stats person can come up with a function that will figure out how to adjust the above error to tell you what % of the ADJUSTMENT you get from Fitbit you can eat... my simple arithmetic skills don't go that far.
Seriously. I have no idea how to construct a function that would be based on a changing value (the difference between Fitbit TDEE and MFP EXPECTED TDEE), which does increase as your Fitbit TDEE increases, but not at the same rate since the MFP expected TDEE stays constant
The error I know how to calculate (18%) has to do with your TOTAL Fitbit TDEE. If you usually have fairly constant activity days, no problem. But if your activity varies a lot it could be an issue as the size of the 18% as a number will increase the more calories you burn
I know that for myself I just accept that on an very active day I probably want to avoid eating back all the way to my TDEE (leave some of the adjustment on the table) and on less active days leave less of it. On average I know that about 100 to 150 Cal of the TDEE I see on my Fitbit doesn't exist. I don't need to be much more accurate than that as beyond that I would go more with how I feel in terms of actual hunger or what have you.
In any case, BASED ON THE FIGURES YOU HAVE MADE AVAILABLE, approximately 500 Cal of your FITBIT TDEE don't EXIST.
HOWEVER, and this is something you've said a few times, THIS DOESN'T MEAN THAT YOU HAVE TO EAT 1000 or 500 Cal less than you've been to lose at two lbs a week. (and let us not forget that I, at least, most certainly do NOT think you SHOULD be losing at 2lbs a week based on your stats!)
Again, BASED, on YOUR figures as given:
To lose 2lbs a week you would have to eat 1000-770= 230 Cal less a day than you have been, or 1500-230=1,270, which is an EXTREMELY BAD IDEA, in my opinion.
To lose 1.5lbs a week you would have to eat 750-770= -20 Cal less a day, i.e. 20 Cal more than you have been, so 1520 Cal a day as opposed to the current 1500 a day which you've given as your actual calories in.
To lose 1lb a week you would have to eat 500-770= -270 Cal less a day, i.e. 270 Cal more a day than you have been, so 1,770 Calories a day.
The figures are TOTAL CALORIES EATEN (NOT NET). And assume that your output (Fitbit TDEE) remains constant at the apparent level of 2812 Cal a day that it was at during the 29 days in question.
1770 Cal a day for a deficit of 500 with a TDEE of 2270 yields an ALMOST SANE and STILL aggressive 22% deficit off your TDEE and would be a much more recommended solution that would have you losing up to 50lbs during the next 12 months.
Consider that the fastest way to get nowhere is to go so hard that the whole things collapses, only to have to start all over again. And from what I remember, you've already tried fast a few times in the past... just saying.
I would also kindly invite the people who I expect will disagree with my negative view of a larger deficit to explain how, IN THIS INSTANCE, when it is known that excess deficits have led to re-starts, it makes sense to continue to try to get to goal with a more aggressive as opposed to a less aggressive approach.
I didn't get alot of what you said but to cover what I did I started logging on mfp on the 17th January so you can discount any 1st week water weight losses. I started exercising on the 27th April I got my fitbit up and running on the 30th April and I do use libra to weigh daily and track0 -
If you're using Libra, is your weight on the morning of 30/4 and the morning of 29/5 your Libra weight trend, or is it your scale weight?
Also, when you counted 43505 calories in. Is that your actual Calories eaten, or are you counting your net Calories in?
Feel free to ask questions if there's something I didn't explain0 -
If you're using Libra, is your weight on the morning of 30/4 and the morning of 29/5 your Libra weight trend, or is it your scale weight?
Also, when you counted 43505 calories in. Is that your actual Calories eaten, or are you counting your net Calories in?
Feel free to ask questions if there's something I didn't explain
Actual weight on scale and calories eaten total had a bad 3 days not logged or weighed grrrr hopefully back on track today 🤞👍0 -
Use your weight level from Libra, not the scale weight, for your calories lost/gained calculation. So libra level on 30/4 and 29/5 vs food eaten between 30/4 and 28/5 inclusive.had a bad 3 days not logged or weighed grrrr hopefully back on track today
make sure your choice of deficit size in not excessive....0 -
13stone 9.1 on 30th April 13 stone 3.5 on 28th May0
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Use your weight level from Libra, not the scale weight, for your calories lost/gained calculation. So libra level on 30/4 and 29/5 vs food eaten between 30/4 and 28/5 inclusive.had a bad 3 days not logged or weighed grrrr hopefully back on track today
make sure your choice of deficit size in not excessive....
13stone 9.1 on 30th April, 13 stone 3.5 on 28th May0 -
And what about the calories eaten?
Could you double check for me that your total Calories consumed truly do end up at almost exactly 1500 a day?
Is your value for weight from Libra, happy scale, or trendweight? Have you changed any of the smoothing defaults (number of days they take into account)0 -
And what about the calories eaten?
Could you double check for me that your total Calories consumed truly do end up at almost exactly 1500 a day?
Is your value for weight from Libra, happy scale, or trendweight? Have you changed any of the smoothing defaults (number of days they take into account)
Value is from libra I haven't altered it at all just whatever settings it came with calories in are correct at 43505. Why use my trend weight in calculations? I started exercising on the 27th so would have been retaining water as I was very sore so that's going to screw up the calculations too?0 -
You use your weight trend precisely in order to reduced the likelihood that the weigh ins you used for your start and end point were artificially high or low on the particular days.
Can the weight trend be more wrong than the scale? YES: if a long term change has recently taken place, Otherwise the long term trend is more likely to be closer to the truth on any given day.
Here is a spreadsheet where you can follow how I would have looked at the information you gave in your posts in this thread:
https://docs.google.com/spreadsheets/d/1_sT5ZzYDAZwdnn0aAPKi8QtudVE2MgwTLuAqpXcpePo/edit?usp=sharing
Or a short link to same: v.gd/hawuwi
Here is a daily spreadsheet I've posted before. Ignore that it talks about Fitbits and trackers. It is just a predicted vs actual daily sheet:
https://docs.google.com/spreadsheets/d/1VDmqNpLPu7sbQSochUJNXdp2F7AN15AGgkvS3zLw1GU/edit?usp=sharing
Or a short link to same: v.gd/rudipa1
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