Calories – Does Heating Margarine in a Pan Result in Loss of Calories?

You can easily calculate a maximum calories difference, and not so easily approximate an actual difference.

If you measure the weight of your meat pre- and post-cooking, you can regard the difference as the maximum amount of fat that has been lost from the meat. Multiply that difference by the number of calories per same unit, and you will have a good idea of the maximum difference in calories.

If you want a more exact number, catch all the drippings and try to determine the percentage comprised by fat. You could boil your drippings for some period, and what is left should be (mostly) fat. That seems like an awful lot of work, but you may be able to do it once and decide that for your purposes whatever you came up with on that one calculation is good enough to apply universally.

Lose It!, a free weight-loss site, has this feature. To use it I think you need to start an account. To access it, you hit the Settings tab and then select Recipes in the left-hand column. Then select "New" and follow the prompts. This calculator allows you to enter the ingredients of a dish you are preparing. Most common ingredients will pop-up in the site's list with their respective caloric values. You can also manually enter in the values if you know them or if the ingredient is not in their list. You then set the "serving size" of your dish as its total volume. Then, when you enter in the amount you are eating into your daily food log, the site automatically shows you the caloric value of your portion.

The fifth screenshot here, shows you what it looks like.