Weight Loss Maths

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BonnieDundee78
BonnieDundee78 Posts: 158 Member
in Health and Weight Loss
OK, so I'm totally onboard with the whole CICO thing. And being a data monkey, I thought I would crunch some numbers to work out my average calorie intake, my daily deficits (i.e. TDEE minus Net Calories) and my total cumulative deficit to date to see whether my total deficit number closely correlates with my actual weight loss. The numbers are... odd.

First off I'm a 39yo, 5ft 3, sedentary female. My starting weight gave me a TDEE of 1834 (I use TDEECalculator.net) and it's been coming down gradually each week in line with my weight. It's currently 1682. My calorie target is 1300 and I was pleased to see that my average net cal intake is nearly spot on at 1286. Yay.

But here's the weird thing: Using my accumulated deficit since Jan 1st (42,731 cals!), I should have lost roughly 12lbs, if 1lb is equal to c3500 cals. But I've actually lost 27lbs. I'd say a good 8lbs of that was water in the first few weeks, so let's say 19lbs. Even that is over 50% more than the maths says I should have lost.

Obviously, I'm not complaining, but I'm curious about why the numbers are so far off. Obviously bodies are weird and none of this is an exact science, but should I assume that my actual TDEE is significantly higher than the calculator suggests? Should I be using another calculator? Maybe I am more active than I think? (although I'm really not; I'm a lazy toad. ;) )

Replies

  • janejellyroll
    janejellyroll Posts: 25,763 Member
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    If you're using a TDEE calculator, it's just an estimate. In your case, it looks as if you are using more energy than your entries on the TDEE calculator would indicate. When losing weight, our calories in and calories out are based on getting as close as we can. But real life data will always show you the more accurate picture and you shouldn't be afraid to change things up based on your real world results (if you think you are losing too quickly).
  • prattiger65
    prattiger65 Posts: 1,657 Member
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    The science isn't off, your calculations are. My off the cuff SWAG is you were/are using more energy than you accounted for. The good news is, you can make an adjustment and eat a little more :smiley:
  • Tacklewasher
    Tacklewasher Posts: 7,122 Member
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    Best guess, inaccurate logging. Your diary is closed so can't really comment on it. Could also be underestimating calorie burn (from exercise and activity).

    You are still losing under 2 lb per week on average (ignoring some water weight), but this may be a bit fast for you (what is your weight and goal weight). Looks at a glance like you should eat a bit more.

    Open up your diary and give us your stats
    Weight
    goal weight
    desired loss per week I think the rest of the stats are there.

    With that someone might have better insight.

    Hey, at least it's a good problem to have :)
  • AnnPT77
    AnnPT77 Posts: 32,738 Member
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    It always makes sense to rule out worrisome health conditions (such as hyperthyroidism), but beyond that, keep in mind that the calculators are estimates, basically giving you the mean of some presumed normal distribution. Standard deviation is relatively small, but way non-zero. This link explains well:

    https://examine.com/faq/does-metabolism-vary-between-two-people/

    Being an outlier is statistically unlikely, but it is possible.
  • cwolfman13
    cwolfman13 Posts: 41,868 Member
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    Firstly, a TDEE calculator is just an estimate...secondly, the relative accuracy of said calculator is only going to be as good as the info coming in. In this case, it would suggest that you've underestimated activity level and thus have a higher TDEE than which was stated...it would suggest that your actual TDEE is closer to 2300 calories.

    What kind of exercise do you do and is that accounted for in your activity level and TDEE? If you're using the TDEE method, it should be.
  • BonnieDundee78
    BonnieDundee78 Posts: 158 Member
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    Excluding my first week (which I class as an outlier because I lost 10lbs!), I've been averaging a 1.3lb loss per week, so the pace of the loss is very healthy. I had 60-70lbs to lose, so it also seems about right for now. I've now got 33lbs to go until I hit my first goal, so I imagine that average loss will keep shrinking as my deficit gets smaller.

    I guess I must be using more energy than I think... but I don't actively exercise at all, and spend most of my day sitting down. I don't count my steps, or log any activity. Definitely a nice problem to have! But if it also means I can increase my calories a little, that would be awesome!

    I'm currently 167.75. Started out at 195. Aiming for 134 (before reassessing!).
  • janejellyroll
    janejellyroll Posts: 25,763 Member
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    BonnieDundee78 wrote: »
    Excluding my first week (which I class as an outlier because I lost 10lbs!), I've been averaging a 1.3lb loss per week, so the pace of the loss is very healthy. I had 60-70lbs to lose, so it also seems about right for now. I've now got 33lbs to go until I hit my first goal, so I imagine that average loss will keep shrinking as my deficit gets smaller.

    I guess I must be using more energy than I think... but I don't actively exercise at all, and spend most of my day sitting down. I don't count my steps, or log any activity. Definitely a nice problem to have! But if it also means I can increase my calories a little, that would be awesome!

    I'm currently 167.75. Started out at 195. Aiming for 134 (before reassessing!).

    You're one of the lucky ones! We see so many threads from people whose estimates are off and they're losing less than they expect, so yours is a nice "problem" to have. :)

    Great progress so far!
  • ccsernica
    ccsernica Posts: 1,040 Member
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    All these metabolic numbers are estimates, based on averages across populations, and they can vary considerably between individuals. You can expect a little wiggle room, unless you've had your RMR professionally measured and know it precisely.
  • Tacklewasher
    Tacklewasher Posts: 7,122 Member
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    @1.3 lbs per week, I wouldn't change a thing and just know something is off but don't change anything.

    Unless it really grates you in which case, make sure you are as accurate on counting calories as you can be and see if you were not overestimating on some things.

    But to me you are doing fine.
  • lemurcat12
    lemurcat12 Posts: 30,886 Member
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    BonnieDundee78 wrote: »
    OK, so I'm totally onboard with the whole CICO thing. And being a data monkey, I thought I would crunch some numbers to work out my average calorie intake, my daily deficits (i.e. TDEE minus Net Calories) and my total cumulative deficit to date to see whether my total deficit number closely correlates with my actual weight loss. The numbers are... odd.

    First off I'm a 39yo, 5ft 3, sedentary female. My starting weight gave me a TDEE of 1834 (I use TDEECalculator.net) and it's been coming down gradually each week in line with my weight. It's currently 1682. My calorie target is 1300 and I was pleased to see that my average net cal intake is nearly spot on at 1286. Yay.

    But here's the weird thing: Using my accumulated deficit since Jan 1st (42,731 cals!), I should have lost roughly 12lbs, if 1lb is equal to c3500 cals. But I've actually lost 27lbs. I'd say a good 8lbs of that was water in the first few weeks, so let's say 19lbs. Even that is over 50% more than the maths says I should have lost.

    Obviously, I'm not complaining, but I'm curious about why the numbers are so far off. Obviously bodies are weird and none of this is an exact science, but should I assume that my actual TDEE is significantly higher than the calculator suggests? Should I be using another calculator? Maybe I am more active than I think? (although I'm really not; I'm a lazy toad. ;) )

    You quite likely are more active than you think if you are putting in sedentary. I lost quite a bit faster than predicted initially, and I think it was just that I hadn't been accounting for that activity (just normal walking around), plus you do drop water weight and my body seemed to want to lose the weight (I know that sounds dumb). (It was a difference of MFP saying 1.8 lb predicted and me averaging around 2.5 even after the initial water weight drop -- I was 5'3, 200, so heavier than you, if my calculations are right.)

    Later I lost consistent with the calculators (when I used Fitbit I lined up well with it, too), so I do think at first it was assuming that I must be sedentary unless I did intentional exercise when I wasn't.

    Anyway, nice problem to have, enjoy it for now!
  • BonnieDundee78
    BonnieDundee78 Posts: 158 Member
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    Smashing. The upside of this discovery is that I don't need to drop my calories to 1200 anytime soon (which I wasn't looking forward to - I like food!). But given that my TDEE is apparently a bit higher than I thought, I probably still have a decent runway to carry on at 1300 (plus some scope for occasional maintenance days!). Thanks all. :)

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