Why does my Calorie Goal keep changing?

It is likely because you have Energy Expenditure turned on. With this setting enabled, your total calorie goal will change accordingly based on your activity. For example, if you burned 400 calories walking with a 1200-calorie goal set, your calorie goal will increase to 1600 after exercising.
​
If you don't like that approach, you can change the settings at any time.
Just tap on the Profile icon at the upper-left corner of the app, and select the Estimation for Energy Expenditure section.
​