Hi Nicole, my guess is that the 2500 would be more accurate than the 1800, unless you're really on the tiny side. Being young, being athletic, and with that much of a workout (cardio and weights), you should be a calorie burning machine. It seems hard to believe you would add a pound of fat in a week. There are a lot of things that can cause weight to fluctuate; maybe water retention for one. Make sure what you eat is healthy (fruits, veggies, lean protein, healthy fats) and you should be good. Keep an eye on it for another week and see what happens, would be my first thought.
"If you drop an egg, you don't say, 'Oh, shoot' and drop the other 11, do you?"
-Source unknown, but obviously brilliant
Reached goal 4/16/2010...but kind of afraid to look these days