800 cal/day?

I'm 5'3" and 105 lbs

A healthy range is 105 - 135.
http://www.shapeup.org/bmi/bmi6.pdf
So you're not underweight yet, but you need to get this eating disorder under control.

My doctor & dietician told me to eat 10x my healthy goal weight in calories to lose weight to get there.
For you, I'd say aim for at least 1100.
Harvard Medical School says to eat 15 cal per lb if you're active about 30 min per day in order to maintain that weight.
http://www.health.harvard.edu/healthbeat/HB_web/calorie-counting-made-easy.htm
For you, that would be 1650.

it's important to NEVER go under your BMR. You should always be eating more than it.
... it is really bad for your body... messes with your metabolism and can really hurt you.

MFP is saying mine is 1705 at my current weight.
For several months I've been eating at 1650, not eating back exercise calories, and my doctors are perfectly happy with my health & rate of weight loss. (Actually, my weight-loss doc is very happy with me, says they rarely see such success, even with surgery, which I haven't had.)

Fat soluble supplements like calcium

A, D, E, & K are the fat-soluble vitamins.
Calcium dissolves in water.
Calcium gets absorbed better with vitamin C, which is why orange juice is often calcium-fortified.
And vitamin D is essential for calcium absorption.

If you don't eat more, you will be in starvation mode and your body will hang on to every calorie you eat.
Eventually it will cause a major weight problem like mine

:grumble:
The body uses fat for energy.
First it uses carbs (glucose, then glycogen), then it uses fat, then it uses muscle.
If she's really been eating 800 cal per day for an extended time, it's quite possible she's burning muscle when the body runs out of the little food she's eating.

_That_ is "starvation mode", and it means that the body is destroying itself to try to stay alive long enough to find food.
We need muscles to survive, mostly the heart & diaphragm.
So if there's any fat available, the body will use that first. It's not going to save fat (which only exists to store calories) & burn muscle (which we need for survival).
She's certainly not going to gain weight eating so little, not at her height.
Hopefully she's been misestimating her consumption & is actually eating much more.

OP, although you are probably still undereating, I think, like most people, you are also probably underestimating how much you eat. Unless you weigh it, if you're genuinely not hungry and there's nothing wrong with you, then you probably are getting more calories than you think. I would estimate between 200-400 more than you think.

edit: I say this because nothing in your log shows any measurements, just subjective things and foods that are notorious for being underestimated.

yep. Are you losing weight? If not, you are eating at maintenance for your current weight.

You're telling someone who is eating 825 calories a day that she's eating at maintenance? If she has an ED, this is just going to confirm her current eating pattern as appropriate.

I take vitamin & calcium supplements.

Fat soluble supplements like calcium wont get absorbed without adequate fat so you can start there, 0.4g per pound of bodyweight.

Yep - a vitamin pill is not a substitute for calories.

Calories are FUEL. Your internal organs are using calories all day long. When they don't get fuel they take what they need from fat AND lean muscle. When they don't get fuel they stop fueling things that aren't necessities.....like the hair on your head.

OMG, that's really low hun. Even if you don't exercise, for your height and weight your calories should be approximately 1300. Definitely increase your calories and try not to use hunger as a measure of eating sufficiently because it's not a great indicator. I don't mean this in a mean way by any means, but if you suspect that you might have an eating disorder then please find a counselor on campus to help. Take care of yourself!

where are the veggies?????

Ummm..she's undereating and THAT'S what you choose to focus on???

If a person eats so little anything to focus on as far as healthy food is concerned is good. Vegetable is a very good food to start with.

I eat a ton of veggies, especially spinach and cucumbers! The calories were just too low to bother adding them to the information I gave.

It is essential to even add things that you might wont add up . for Years I was a raw vegan, and believe me when i say cucumbers, kale, spinach etc etc add up to alot. Everything adds up.

OP, although you are probably still undereating, I think, like most people, you are also probably underestimating how much you eat. Unless you weigh it, if you're genuinely not hungry and there's nothing wrong with you, then you probably are getting more calories than you think. I would estimate between 200-400 more than you think.

edit: I say this because nothing in your log shows any measurements, just subjective things and foods that are notorious for being underestimated.

yep. Are you losing weight? If not, you are eating at maintenance for your current weight.

You're telling someone who is eating 825 calories a day that she's eating at maintenance? If she has an ED, this is just going to confirm her current eating pattern as appropriate.

Nope. We're saying, if she is not hungry and not sick, then she is more than likely eating more thAn what she thinks she is, probably closer to 1000-1200 calories minimum.

....which is still too low for an 18-year-old girl. That's what I eat, and I'm short and 55.

OP says her weight stayed the same throughout the summer. This means she was eating at maintenance. Either she has a much lower calorie requirement than you are assuming, or she is underestimating how much she is eating significantly. Either way, she is not losing weight - so she is not eating 800 calories, and she is not starving herself. "Estimated numbers" say nothing compared to real results.