what happens if you're under 1200 calories a day (even under 1,000 a day), but are getting LOTS of nutrition?

I know metabolism slows if you drastically reduce your caloric intake (below 1200, say)... but I keep hearing that's because you'll have a hard time sticking with it, that you can't get enough protein... enough of the nutrition you need...

But I've found since I started really keeping an eye on what I eat that the foods I like best are naturally high in protein and/or high in vitamins and dietary fiber... but low in calories. I was a jerk to eat the way I did to get me heavy in the first place.

My scores on the Food Log analysis are always great big shiny As. I'll chop up an entire stalk of broccoli (60 calories there), mix in a cup of mushrooms (I think that's another 30) and a couple of chopped up roma tomatoes (again, about 30)... top it with 3 egg whites (45 at best)... maybe even a salmon patty (80), and that is delicious to me. I don't want any butter, any dressing, any salt.... that's just good eatin'. And a TON of food. And under 250 calories, and I am then stuffed for a good long time.

Breakfast is always an entire grapefruit (120), and maybe a WHOLE egg (not just the white), and then I snack on fruits and veggies all day. I'll throw in a South Beach Living meal replacement bar or a lean cuisine to make up a third meal...

and I'm still way under 1200 calories. And tons and tons and tons of "A"s on my report card.

Does metabolism always necessarily slow down if your calorie count is low, or does what you've eaten make up the difference?

(I feel like such a newb.)

Yes, your metabolism will slow down if you continue to eat that little.  You're getting As on the report card because it tends to give high marks for all fresh fruit and veggies (as they are good for you) - but it doesn't really look at your carb/fat/protein balance to see if it's reasonable.

On that diet, you cannot possibly be getting enough fat.  The only source of fat I saw was the "maybe egg" and the "maybe salmon".  You should be getting 20-30% of your calories from healthy fats (like the egg and salmon - or nuts or avocado or olive oil, etc.)  Your body needs them to repair cell membranes, keep your skin healthy, etc.  I also didn't see much calcium or iron in your diet - which could cause health problems too. 

You're full because you're eating a lot of fruit and veg - which are bulky.  To increase your calories, you need to eat some less bulky food too.  Most fat sources are calorie dense, so increasing your fat intake will kill two birds with one stone. 

I'm EXACTLY the same way as you. I was raised on dinners that were just a huge, delicious salad with tuna mixed in for protein... The meals/diets you describe are basically the same as mine, and I have the same problem!

But it's true that you're not getting enough fat, calcium, and probably not enough protein either. Even though I was getting plenty of healthy foods, without protein and stuff i still felt pretty weak and stuff throughout the day, so I'm drinking protein powder along with breakfast (I love Designer Chocolate, 18 g protein and an added 100 calories per serving, and sooo good) and almonds or some other type of nut throughout the day for fat. Also eat more fish or lean chicken, both add calories, good fat (well, not so much for the chicken, but you still need more fat anyway), and protein. And drink fat-free milk/yoghurt for protein and calcium as well....adding those to my fruits/veggies/healthy foods diet has really helped, and I feel way stronger and more energized and stuff...good luck :)

also, may I say that while the food you are eating is nutritious, that does not mean that your body is getting all of what it needs or enough of what it needs.

  The nutrition grade is an average of all the grades for individual foods, taking into account the weight in grams of each food.  therefore, as a clif bar is and 'A' and so is broccoli... you can eat only clif bars all day or only broccoli all day and still receive and A score.  That is clearly not a great way to eat... not balanced at all.

A 'healthy' diet should be varied, nutritious and provide you with enough energy.  If you're getting the first two but not the last one it's not a healthy diet..... 

Thanks for all the feedback, everybody.

The only bit that still has me feeling confused is that I "should" be having less energy on what I'm eating.  But I'm full of more energy than I've had in years.  I can walk for miles and enjoy every step, whereas I used to lumber along... and I definitely take advantage of it.  I'm working out whenever I have a spare minute, and generally being active even when I'm passive.  (i.e., I'll flex my thighs or something if I have to be sitting for awhile - say, on the bus)

Everyday I do a little bit more, and everyday I've been eating a little fewer calories, until I realized (today for example) that this might bite me in the butt so far as metabolism goes.

Or am I misunderstanding what energy is?

I think you're confusing 'energy' with 'vitality'..   Better food & better nourishment will give you more vitality because of the vitamin and mineral content.   Energy is fuel.  You need so much each day to enable your body/brain to function properly and it is measured in calories.  

It's rather like fuelling a car.... if you put top-grade petrol in the tank your car will purr along much more happily than if you put in low-grade rubbish.  But if you only fill the tank half-full, it'll conk out well before you reach your destination.   Eating fewer calories each day is the equivalent of only filling half the tank.   Bodies don't conk out straight away because they're cleverer than the internal combustion engine.  Instead they slow down the rate at which they burn the fuel and then they'll start to leech the missing energy from your muscles and vital organs.  Eventually the chronic lack of food means that they start to miss out on nutrition.  Then they really struggle.  Then they conk out.

The healthy combination is nutritious food to give you vitality in sufficient quantity to give you energy.