Calories Consumed = Money Spent
Calories represent the amount of energy that is contained in food. The more calories that you consume over your daily metabolism, the more weight you will gain.
In our comparison, we can visualize calories as the equivalent of money. Each time you consume calories, you are spending money from your daily budget (metabolism). So the primary goal is to not overspend more than you are allowed each day, otherwise, you will go into debt (gain weight).