I will have bad days, and then all of a sudden I will have a good day where I fell really good when I run. Usually this is because I take more effort to drink a lot of water earlier in the day. If a workout, such as running, is easier than usual for any particular reason, does that mean I’m not using as much energy as when I’m ‘suffering’ more? Thanks!
It all depends. Burning calories depends on 2 main factors: The effort and the weight of the person. The harder you work, the more calories you will burn. The more you weigh, the more calories you will burn. Google a Calorie Calculator to get a more exact amount of calories that you will personally burn.
So to answer your question, yes, you probably aren’t burning as many calories. If you are running the same distance, and are weighing less, you need to run faster to burn the same amount of calories. However, as a counterpoint, the less you weigh, the less calories you need to burn.