Should you eat the calories gained by exercise?

2500 calories weekly is a lot . . . how much are you hiking, in what kind of terrain? How did you estimate the exercise calories?

Regardless, the true test of whether we're under/overeating is weight loss rate on average over 4-6 weeks . . . whole menstrual cycle(s) for those who have them. If you're losing more than 0.5-1% of current weight per week (with bias toward the lower end of that unless severely overweight), then eat more. You can estimate how much more (or less) to eat by assuming that 500 calories daily is a pound a week bodyfat change.

The MFP estimates will be close for most people, but some people will differ from the group averages that MFP (or other calculators/trackers) spit out. On top of that, all of logging involves estimates. We can be close enough to be useful, but the "useful" can depend on adjusting goals based on personal experience.

I ate all my exercise calories all through loss (50-some pounds) and 7+ years of maintenance since, after estimating them carefully. According to Garmin, I averaged only about 1660 calories per week, for an average of 6 weekly hours of exercise, mostly rowing (boats & machines) and biking (ditto). I'm glad I took that approach, because my exercise varies seasonally and with weather . . . it's helpful for maintenance to have a reasonable estimate of calorie needs for varying levels of exercise.