Ann uses 150 fewer calories by skipping tennis. She eats popcorn and chips, adding 500 calories. What has that done to her energy/calorie...

The sense of your question is that you wonder how much
damage is done by ingesting 750 calories over and above your normal maintenance
diet.

By focusing on calories you are recognizing how
important they are in terms of maintenance of body weight.  Exercise burns calories, and
food contains them.  And it is the net total calories ingested daily over time that
determines your body weight.

Here are the most important
basics that will allow you to understand and work with
calories.

First of all, the human body requires
approximately 15 calories per pound per day to maintain weight.  This is true regardless
of height or sex.  A 200-pound man can eat 3,000 calories daily without gaining weight. 
If he exercises he can eat even more.

Second, when dieting,
in order to lose weight at a recommended rate of one pound per week, you will need a
daily deficit of 500 calories.  So if your daily maintenance is 1500 calories, for
example, you can lose one pound per week by a daily diet of 1000
calories.

Conversely, by ingesting 750 excess calories per
day over time, Ann would be expected to gain approximately 1-½ pounds per week…not a
good thing!

The reference provides a calorie calculator for
women. It is very useful in formulating a weight reduction plan.