Exactly. My BMI is ~21, and I eat 3,000cal a day most days. The difference is, I have run a little over 1,000mi so far this year, and biked almost 7,000. I also lift weights 4x a week. It's not uncommon for me to burn over 4,000cal in a day (3,635 yesterday according to my Garmin data, 28,000 steps (ran 7mi) also biked for an hour and a half), and I weigh 129lbs as of this morning right after I peed.