Weight loss as a math problem, but which numbers are wrong?

subversive99

Ok, so being a bit of a nerdy guy, I've decided to approach this whole thing as a bit of a math exercise. I have been tracking my calories in since early January, and wearing a fitbit one (no HRM) everywhere. I enter weightlifting exercise (following SL 5x5) into fitbit's portal, but do not enter running excercise, as I figure it will do a decent job of calculating my calorie burn based on the increased number of steps taken during the running periods.

I'm 5'8", 256.6 pounds as of this morning, for reference.

With 28 days of data under my belt, I have following numbers so far.

Starting weight (January 9th): 261.6
Total Calories Eaten per tracking: 59,255 (2116/day avg)
Total Calories Burned per fitbit: 94,930 (3390/day avg)
Total Deficit for 28 days: 35675
Total expected weight loss for 28 days: 10.19/lb (based on 3500 calories per pound)
Actual weight loss for 28 days: 5.0 pounds

Ok, so I have a couple of questions around these numbers.

1. When do I start to investigate which is wrong, either my food tracking, or my fitbit is over estimating? Is 4 weeks enough?
2. I've looked around at a number of TDEE calculators, and they all spit out a number pretty similar to what the fitbit is telling me (ie: in the 3300-3600 range), so I don't know that I necessarily want to assume the fitbit is over estimating, so then...
3. ...It must be my food tracking? Honestly though, I have tracked literally everything I've eaten. So let's assume that there is some margin of error on the food just based on the fact that not every burger at a restaurant is exactly the same number of calories as the nutritional info lists, and manufacturers could have a margin of error on their packaged foods too. So what margin of error is reasonable to assume? 10%? 20%? Even assuming every single thing I ate was actually 20% more calories than listed (which seems unlikely), I still get an estimated loss of 6.8 pounds. Which brings me back to my first point, which is....
4. ...how much data is enough to be a trend that evens out with regards to the human body, water retention, when you last pooped, etc etc? Is 4 weeks enough, or should I re-evaluate in another 4 weeks?

Just for the record, I'm not freaking out or anything about this. I'm staying the course and understand that 5lb in 4 weeks is still pretty good. I realize this is a rather long and detailed post, but I'm trying to provide all the info people could need in order to provide a quality response. Thanks!

in_the_stars

Revisit and revise when you look in the mirror. I know you're looking at it as an exact science. Quantifiable?

Best of luck to you.

TimothyFish

First, the calories listed on packages is based on an average of several similar items. Second, it is difficult to determine calories burned from number of steps. While you could look at it as a science if you could measure calories accurately, the typical person can't. Look at it more like an art. If you aren't losing enough, then reduce calories in or increase calories out. If you're losing too much, then do the opposite.

ndj1979

MrM27 wrote: »

There is a pretty simple answer to your dilemma.

First, there will always be some sort of error is food logging. We are never 100% spot on. Our goal is to be as close to accurate as possible.

You just started out with weight training which will cause your body to retain water which will mask losses that should reflect on the scale. You need water retention, it will always be a factor.

Fitbit is not going to give you an accurate number of calories burnt because it's designed for aerobic activities not NEAT.

I say go with the plan of waiting another 4 weeks. Keep it up. Good start so far.

go with this OP …

and for my contribution, I think your fit bit is overestimating your burns….

however, five pounds over 28 days is a tad over one pound per week loss, so you are doing fine. slow and steady wins the race.

Keep eating in a deficit, and keep lifting….

RodaRose

Your plan will work out for you eventually -- just not on your time line.
Expecting to lose 10 pounds in 20 days is optimistic.
The margin of error is great.
If you need tangible feedback that the scale is not providing you, take lots of pictures and measurements.
(I apologize for not responded to you numbers questions)
Stay focused and keep to your plan. You will get the pay off you want.
Reevaluate/ reassess in four weeks.

myfatass78

Good job so far. There is one thing I see when I look at your diary that might be causing some issues. There is a fair amount of processed food and things like beef jerky and burgers. These have HUGE amounts of sodium in them which will cause water retention. It might be skewing your results. Not a criticisim of the diet itself but just the salt content.

honkytonks85

I wouldn't trust a fitbit.

loulamb7

Glad you're not freaking out. Weight loss isn't linear and too many variable can effect our weight other then fat. You may see an unexpected drop. Start tracking body measurements and photos for comparisons. Keep up the good work.

PokeyBug

I'm a little bit like you... I want to get as exact as I can. However, I totally realize that it's never going to happen that way. I don't trust FitBit or those other devices, and I know that my 'calories burned' calculators are not always very accurate. As such, I have decided not to count my exercise calories at all. I've figured my TDEE without exercise (1440, because I'm SHORT), and I eat within 200 calories of that amount. I still figure my exercise on MFP, mostly just to keep track of what I've done and if I'm meeting my weekly goals. But I DO only eat it back under special circumstances, like Christmas dinner or my monthly date night with my husband.

I'm satisfied with losing 1/2 a pound a week, happy with losing 1 pound, and I'm over-the-moon ecstatic with losing more than a pound. For a very long time, I was over-the-moon ecstatic every week, but, now that I'm under 130#, I've been either satisfied or happy for the most part. Some weeks, I'm just okay, since I didn't gain or lose.

My advice, now that I've reached a third paragraph, is, if you're not satisfied with how you've been losing so far, make sure you're recording your food intake very accurately, and, if you've been eating back some of your exercise, stop doing that for a couple of weeks. See what happens. What works for me might not work for you, but it might. *shrug*

ndj1979

OP - are you doing MFP method or TDEE method?

IF MFP method and you are doing SL 5x5 you may want to just switch to TDEE method and then you do not need to worry about inputting calories burned and eating them back …

I find TDEE method to be better because once you nail your maintenance number you know how much you need to eat to gain, lose, and/or maintain.

in_the_stars

MrM27 wrote: »

in_the_stars wrote: »

Revisit and revise when you look in the mirror. I know you're looking at it as an exact science. Quantifiable?

Best of luck to you.

OP, ignore that. Doesn't make sense anyway

LMAO! Yes, EMT. lol

lynn_glenmont

I've done this. Actually I've done this twice, over 8 weeks in the fall of 2013, shortly after starting MFP, and over 9 weeks in the fall of 2014. But I did it to calculate my NEET (the amount of exercise I get from week to week is way too variable to go with TDEE), and got a number more than 200 calories higher than MFP calculated in 2013, and a number about 400 calories higher than MFP calculated in 2014. It didn't send me down some rabbit hole trying to figure out what I was doing wrong. I did a mental happy dance -- more food if I want it, more weight loss if I don't. No need to try to stick to the miserable 1460 calories MFP originally suggested.

Instead of assuming the TDEE calculators are right, why not just assume your logging of calories consumed is correct, add the 59,255 calories you ate over four weeks, the calorie equivalent of the five pounds you lost (17,550), and divide by 28 to find your "real" TDEE of 2740. Even if the TDEE calculators are right and there's something wrong with your logging, isn't it a whole lot simpler to use the TDEE that reflects the way you log, rather than to try to figure out where the mysterious problem(s) is/are in your logging, and then try to find a way to correct them? Your TDEE is 2740 "OP calories," where "OP calories" are the units in which the OP measures the energy in food and the energy his body uses.

I went with 8 weeks of data because I'm a woman, and I wanted to smooth out the hormonal fluctuations. I would think 4 weeks of data would be enough for a man, but, hey, in another 4 weeks you can toss two months of data together and see what you get.

Best of luck. Embrace the numbers.

subversive99

Interesting stuff folks. Thanks for all the responses, I'm just out for the evening, will answer relevant questions people had tomorrow.

salzamora

I think you have done a great job, five pounds in 28 day – well done. Can we spin this algebra problem around a little?

You have a good four-week base line here. If you take your total net calories eaten of 59,255 plus your calories attributable to weight loss of 17,500 (3,500 * 5 lbs) you get a total of 76,755 (59,255+17,500) or 2,741 calories/day. This 2,741 represents your average maintenance calories; the net amount you would have had to consume to not gain or loss any weight.

Now this amount will change as you keep losing weight so if you calculate what this amount is every week using the previous three week, so a four week rolling average, you will be able to estimate what your goal net calories should be in order to lose X pound(s) per week (deduct 500 calories/day for 1 lbs [3,500/7 days a week], deduct 1,000 calories for 2 lbs [2*3,500/7 days a week]) – I personally think shooting for two pounds a week is very difficult.

Is the fitbit accurate? I don’t think it matters as long as it is consistent and you are consistent in your logging of calories. I initially lost 40 pounds using this formula and I gained 12 of them back over the holidays (stopped exercising and stopped logging my food). So since 26 December I have lost 10 of the 12 pounds using this formula. I hope this will work for you.

segacs

I'm also a math nerd and I like the way you think.

The variables I see that could be off here are:

• Like others suggest, you could be underestimating your food intake.
• Logging your weight training and eating back those calories could be throwing you off. Strength training is important to your toning and muscle retention, but it doesn't burn a lot of calories in and of itself. Maybe log and eat back only your cardio calories?
• Weight loss isn't linear. It fluctuates in a range of several pounds. Maybe your first-day weigh-in was at a low moment and your 30th-day weigh-in was at a high moment? Have you tracked your trend?
• Fitbit, TDEE calculators and MFP all are going to estimate your calories burned based on formulas and algorithms. All of these may not correspond exactly to your body.
• TDEE fluctuates daily because you move different amounts each day. There's no single TDEE number for each person; instead, we each have a range.

I agree with Lynn; why not just calculate your actual "observed" TDEE range based on the data you have seen thus far, and assume it's somewhere in there?

Cortneyrenee04

You mention restaurant meals. I think if you want your data to be as accurate as possible, you'd have to make 100% of the food you eat. You have pretty much no idea what's in the food that someone else prepares.

Good luck