Severely underestimating my calories?

bfbg1121 · March 2020

I'm an 18 year old girl, 5'3 and 102 lbs. MFP tells me I should eat 1520 calories a day, and my Apple Watch tells me I only burn ~1500-1600 calories a day in total. However, I track around consuming 1700-1800 calories most days and sometimes I even lose weight on this amount.

I work out at home for about 20-30 mins 5-6x a week and go for a 30-40 minute walk every single day. I sit a lot at school but when I'm not at school I stand whenever I can and am constantly moving.

How is it possible that BMR/TDEE calculators, MyFitnessPal, AND my Apple Watch all tell me I should consume 1500-1600 cals bc that's how much I burn supposedly, yet I eat more than that and don't gain weight (& sometimes lose weight)? Is this bc I'm young so my metabolism is fast? Super confused & can't find anything online about this.

bfbg1121 · March 2020

I also have a history of disordered eating in the past so I would assume my metabolism would be much slower bc of that. That's why I'm really thrown off.

freda666 · March 2020

If you are losing weight and do not want to then you need to eat more regardless of what the computer tells you do do.

PAV8888 · March 2020

The estimates we use are based on statistical models which means that by nature they will be very accurate for most, slightly less accurate for some, very inaccurate for very few.

Your particular height and BMI may match some less current statistical models better than it would match more current models that were developed using a mix of people of higher BMI.

The estimates you get for maintenance are substantially based on the inputs that you give.

What YOU perceive as sedentary or lightly active, or active or whatever the name the model calls for does not necessarily match the model authors' definitions. The fact that you are standing and moving around a lot is likely to be having a major effect. Whether that's conducive to your longer term goals is an open question.

It really doesn't matter what any of the models say, your average weight trend over a 4-6 week period that includes a complete hormonal cycle--something which you then look at month after month after month is what will determine your progress.

Given the history you alluded to I would imagine you would have a goal of getting closer to BMI 20 so as to be fairly confident you were truly weight restored as opposed to exposing yourself to the risk of a roll back by hanging around the underweight territory where you're still currently finding yourself.

Depending on where you're coming from it is not unheard of for a person who is trying to restore their weight to go through a period where they would require significantly MORE (not less) calories than a person without any history of ED to gain and then maintain a certain amount of weight. This is usually normalized several months after full weight restoration.

AnnPT77 · March 2020

PAV8888 wrote: »

The estimates we use are based on statistical models which means that by nature they will be very accurate for most, slightly less accurate for some, very inaccurate for very few.

Your particular height and BMI may match some less current statistical models better than it would match more current models that were developed using a mix of people of higher BMI.

The estimates you get for maintenance are substantially based on the inputs that you give.

What YOU perceive as sedentary or lightly active, or active or whatever the name the model calls for does not necessarily match the model authors' definitions. The fact that you are standing and moving around a lot is likely to be having a major effect. Whether that's conducive to your longer term goals is an open question.

It really doesn't matter what any of the models say, your average weight trend over a 4-6 week period that includes a complete hormonal cycle--something which you then look at month after month after month is what will determine your progress.

Given the history you alluded to I would imagine you would have a goal of getting closer to BMI 20 so as to be fairly confident you were truly weight restored as opposed to exposing yourself to the risk of a roll back by hanging around the underweight territory where you're still currently finding yourself.

Depending on where you're coming from it is not unheard of for a person who is trying to restore their weight to go through a period where they would require significantly MORE (not less) calories than a person without any history of ED to gain and then maintain a certain amount of weight. This is usually normalized several months after full weight restoration.

^^^ All of this.

In support of the "calculators & devices just give statistical estimates, that can differ from individual reality" piece of it:

I've been logging eating/exercise/weight pretty carefully for almost 5 years now, and wearing a respected-brand fitness tracker for well over a year. MFP and the fitness tracker, both given accurate set-up information including accurate activity level in MFP, each estimate my calorie needs several hundred calories per day lower than my personal data logging data says. This is unusual, but it happens. There need not be an obvious explanation (reassuring as it might be to have one).

PAV, in the post above, gives some useful caveats about needing multiple weeks data among other things, but within those guidelines, carefully-kept personal experience data should be understood to be more accurate than statistical estimates from MFP, online calculators, or fitness tracker devices, IMO and IME.

sijomial · March 2020

Think of a bell curve - the average will be the middle, the majority of people will be grouped around the middle but there's outliers in both directions.

Although you are comparing different numbers they are all based on a small group of statistical studies which attempt to estimate the average.

Sailrabbit.com calculator lets you see results from 6 different studies but in the end, especially if you are an outlier, actual results over time trump estimators.

BTW - this description doesn't sound very average to me!
"I work out at home for about 20-30 mins 5-6x a week and go for a 30-40 minute walk every single day. I sit a lot at school but when I'm not at school I stand whenever I can and am constantly moving".

GaryRuns · March 2020

PAV8888 wrote: »

The estimates we use are based on statistical models which means that by nature they will be very accurate for most, slightly less accurate for some, very inaccurate for very few.

Your particular height and BMI may match some less current statistical models better than it would match more current models that were developed using a mix of people of higher BMI.

The estimates you get for maintenance are substantially based on the inputs that you give.

What YOU perceive as sedentary or lightly active, or active or whatever the name the model calls for does not necessarily match the model authors' definitions. The fact that you are standing and moving around a lot is likely to be having a major effect. Whether that's conducive to your longer term goals is an open question.

It really doesn't matter what any of the models say, your average weight trend over a 4-6 week period that includes a complete hormonal cycle--something which you then look at month after month after month is what will determine your progress.

Given the history you alluded to I would imagine you would have a goal of getting closer to BMI 20 so as to be fairly confident you were truly weight restored as opposed to exposing yourself to the risk of a roll back by hanging around the underweight territory where you're still currently finding yourself.

Depending on where you're coming from it is not unheard of for a person who is trying to restore their weight to go through a period where they would require significantly MORE (not less) calories than a person without any history of ED to gain and then maintain a certain amount of weight. This is usually normalized several months after full weight restoration.

In particular pay attention to the highlighted statement. When you say I track around consuming 1700-1800 calories most days and sometimes I even lose weight on this amount you can't base judgments on what is happening with your weight day to day. You have to use a trend over a number of weeks. Your weight can vary quite a bit from day to day based on hydration and food digestion, but over a number of weeks how your weight is trending will tell you where your calorie level is at, deficit, surplus or maintenance.

Below is an example of my weight as obtained via TrendWeight. See the spikes? Those are my actual scale readings. They jump around like crazy but you can see that over the 3 month period my weight has been decreasing. That's because, on average, I've been in a calorie deficit, eating fewer calories than I'm burning. Even the trend isn't particularly smooth. You really need to look at the big picture to see that I am in fact losing weight. And I'm a guy. I don't have to deal with the hormone variations women have to deal with AND I eat the same exact thing 5 days a week. And still my weight varies significantly from day to day. So use something like Libra, TrendWeight, or Happy Scale and see what your weight is doing over 4-5 weeks before you start adjusting your calories too much.

Pipsqueak1965 · March 2020

You sound pretty active, and you are very young - these are both good reasons to be needing the amount of calories you eat, and more if you are steadily losing weight.

Severely underestimating my calories?

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