Calories in cooked foods vs. raw

I have a question..
Do foods lose calories when you cook it?

For example,
If you boil chicken, the water will end up having like 5 calories or something
Does that mean the chicken itself LOST 5 calories?
It only makes sense, since there's no way the meat somehow magically GAINED calories..

yes that makes sense. some of the fat in the chicken would mix in with the water, therefore, the chicken has less fat.

I know the glycemic index of foods such as carrots, grains and pasta changes when they are boiled, but as far as calories go I can't say.

It depends on what you're cooking and how you're cooking it.  If you boil dry pasta, for example, the calorie count doesn't change but it becomes heavier because you've added water.  If you make toast, the calorie count of the slice of bread doesn't change but it will weigh less because it has lost moisture.  If you grill a piece of meat and some of the fat runs off then the calorie content of the meat has reduced as well as the weight.  If you cook meat in a casserole some fat will come out of the meat and into the casserole juices... so none lost in total.  If you saute, fry or brush meat with oil or butter before cooking you have to add that in as extra calories.

So does this mean that in theory, let's say I grill a chicken breast that started out as 8 oz, but when cooked was only 7. Should I only be logging 7 oz or logging the pre cooked weight?

This is a really complicated question.  It depends on what food you are dealing with.

For meats, my understanding is that the calorie count numbers are for cooked weight.  A 4 oz raw piece of chicken becomes about 3 oz cooked weight.  It loses water as it cooks, so the calories by weight are higher in the cooked food.   But lucky for us cc posts cooked values.  When I work from uncooked weight, I assume 25% weight loss to get the cooked weight for meats. 

For starches (rice, pasta, potatoes, beans, cereal, split peas), the dry food gains water while it cooks.  And as a result, the calories for the cooked weight are a lot lower than dry weight.  But something else happens, too.  When heated the starch granules rupture, releasing the starch in a form that is more easily digestible.  So the more you cook a starch, the higher the calories and glycemic index are.  If you were to crunch up a handful of uncooked rice or oatmeal or a raw sweet potato, the calories would be way lower than eating it cooked. [It's very hard to find information on the magnitude of the cooking effect. However, the following link gives information on digestive sugar release from starchy mung beans http://beyondveg.com/tu-j-l/raw-cooked/raw-co oked-2a.shtml  The sugar release from completely cooked (pressure cooked) beans is twelve times higher than from uncooked - for normal cooking it is only five times higher, suggesting a significant "al dente" effect.]   In theory the same thing happens when you eat spaghetti al dente, but I don't know how to adjust the calories down for undercooking. I use the number listed on the package (which for spaghetti is based on the dry uncooked weight).  That gives a safe calorie number, on the high side of reality - only really accurate if you're eating canned spaghetti.

To convert a dry starch food weight to a cooked one, I'd use a four to one weight ratio as a general rule.  An ounce (27g) of dry pasta or rice is about four ounces cooked (100g, or volumetrically about a packed half cup measure), and about 100 calories.

This is very helpful. I thought I was having to log an awful lot of cals for my meats!

I also wondered about that. But what if you're not boiling vegetables but you're steaming them? I don't even know how to log it in the food count thing. Does it still retain the calories it did when it was raw?

If you want to be consistent start with the raw, dry or uncooked food.   When you buy anything in a packet, the calorie count on the nutrition label is the food 'as sold' unless otherwise stated.  And if you log a recipe with CC then you're always using the raw counts. 

Boiling or steaming vegetables I 'd use the same calories.  The calorie determinations in the lists are for total calories, based on the weight of carb, protein and fat in the food.  The more you cook them the higher their digestibility, especially for the starches.  So a starchy food like peas would have the same total calories as cooked peas, but a lot of those calories would not be digestible in the raw peas.  Assuming the calorie count is correct should give a safe high estimate of the digestible calories in any food. 

Now you've got me thinking about raw snow peas as a diet food, and it's lunchtime....and all I have is this can of tuna.....

Well either way, the calorie deficit isn't enough to make a big difference. I was just curious because I noticed that chicken broth (or even vegetable broth) had a lot of calories even though it's pretty much just boiled meat juice!

According to the USDA 1 unit (yield from 1 lb ready-to-cook chicken) of raw chicken breast meat has 78 kcal, and 1 unit (yield from 1 lb ready-to-cook chicken) of stewed chicken breast meat has 86 kcal. 

http://www.nal.usda.gov/fnic/foodcomp/search/