Eating Too Little

[HostingOfDawn]

Age:15

Height: 5 foot

Weight: 99-100lbs

Exercise: 1 1/2 hours walking Pace// nearly 20 min per mile. 10k steps. 

Well, Fitbit says I need 1400 calories per day to maintain. I walk at a very fast pace every morning at 4:30 for an hour and a half (roughly 10k steps) . When I use other calories estimate calcs, they say I need around 2000 calories per day. Which is right? 

[MrMarv]

@HostingOfDawn - 

I am a computer programmer, not a doctor or nutritionist, however...

If I understand the question as being "What is the minimum calories I need to consume the replenish the calories burned through exercise and just keeping alive, with no need to either gain or lose weight?" then here is my take. But we have to look at four things - though you don't one of them and we will assign that thing a value of zero.

Keep in mind the Fitbit 1400 calories to maintain and that there are 1440 minutes in the day.

First the just keeping alive calorie burn - it's called your BMR or Basic Metabolic Rate. For a pretty good estimate of that value look at your calorie burn estimated by Fitbit during your sleep time either on the web or on the Fitbit app. I suspect it is about 1 calorie per minute by what you have stated in your post. Mine is 1.2, but I am 65 years old, 5' 11" and 190 lbs.

Now you know where the 1400 calories a day that Fitbit talks about comes from. But that is only valid if you lay in bed 24/7 and you don't.

The "thing" I mentioned that looks like it will be zero, is the deficit calorie count needed to reach a person's weight goal. Mine is 500 calories because I want to lose some weight gained after surgery which was also over the holidays. Only five pounds gained in two months, but I want it off fast. I should reach my goal by the end of this month.

Your Fitbit tracker includes BMR in all of it's calorie burn calculations so you don't have to worry about that. You only have to worry about BMR towards the end of the day when you want to know how you stand for the day.

Here is a snapshot of my food page on my phone from I believe yesterday. I say believe because it comes from my "image bank" here at Fitbit and for the purposes of this discussion we don't need to know exactly what day the image was captured.

At 2:41 pm there are 9 hours and 29 minutes left in the day, or 569 minutes. My remaining BMR is 683 calories. Taking that and my deficit and the calorie values on the food page gives us:

Remaining BMR + Calories burned - deficit - Calories in = Calories left to eat

or

683 +1691 - 500 - 1271 = 603

603 is pretty close to the 572 displayed. Remember the BMR I use is estimated from a chart with rounding.

So for you, let's pretend it is 8:00 pm and you are trying to decide if you should eat that slice of chocolate cake (300 calories) for desert or maybe even "Need to". And pretend your BMR is 1 calorie per minute, you have burned 1300 calories and eaten 1100 calories.

Your remaining BMR is 240 (4 hrs * 60 min * 1 cal per min) that gets added to the 1300 calories already burned for a potential burn of 1540 for the day. Subtract the 1100 calories already eaten and you have 440 calories left to eat to stay "even". 

Eat that cake and have a glass of 1% Lactaid Milk at 110 calories to go with it and you are pretty close to even.

I sure hope the above helps. Feel free to share my explanation with someone who's opinion you trust, parent, teacher, best "geek" friend, or whomever. And if is the "geek" friend, send along my regards as a fellow "geek".

[HostingOfDawn]

Well, It says I can have 1400 a day If I am walking my 10k, If I do not, it is around 1200. Which just seems...So low

[MrMarv]

@HostingOfDawn -

Even if the 1200 calories without meaningful exercise represents your BMR, then that would be about .833 calories a minute. 

Yes, you are 1) female and 2) quite slight of build so your BMR would be quite a bit lower than my 1.2 and my wife's 1.1. So maybe .833 isn't too bad of an estimate.

Even so, there is one more place to go to see if Fitbit is using something else to skew the "what you can eat to maintain" number.

Go to the web dashboard and click on the Log tab - it is highlighted in blue below:

On the Food log page you will see the Food Plan panel just above the daily summary.

Clock on the right arrow twice until you get to the Plan Summary panel:

Remember that Calorie deficit I was writing about in my previous post. Mine was 500 a day because I wanted to loose 5 pounds gained after recovery from surgery and the Holidays. If you have a number there then Fitbit is subtracting that value from what you can eat in an attempt to help you loose weight, which you have stated you do not want to do.

Let me know if there is a number where mine says -500, including the plus/minus sign.

[MrMarv]

@HostingOfDawn - 

If you are using an iPhone like me or possibly an Android phone dashboard, there is maybe a quicker way to determine what is going on.

1. Make note of your calories left on your food tile.
2. Touch the Account icon at the top right of the dashboard.
3. Scroll down to "Nutrition and Body" and press it
4. On that page under "Weight" does "Your Goal" say "Maintain"? 
5. If not, let me know later what it says, but press on it and then select Maintain.
6. When you do that, it will display what it thinks is your current weight and display it.
7. If that is indeed the weight you want to maintain press save, otherwise scroll the ruler to select the weight you want to maintain and then press "Save"
8. When you get back to the Goals page, press on the dashboard icon to return to the dashboard.
9. Force a sync to the Fitbit servers by dragging down on the dashboard and releasing.

After all of that check your calories left on your food tile and see if there was an appreciable change.

Hope this helps. Let me know.