Trying to determine calories is the hardest thing - it pretty much boils down to trial and error. When I started counting calories, I went strictly by the values I got on The Daily Plate - based on height, current weight, activity level, and weight loss goals. I was up around 2200 calories per day, I believe. I thought "Wow! This is great - look at all the food I can eat every day! It's like I'm not even dieting at all!". That also meant I wasn't losing at all either and I quickly fell off the wagon. This time around, I played with the numbers until I was losing consistently every week and that's where I've held steady. It's between 1600-1700 per day and I will adjust again when my loss starts to stall. Your nutritionist must have a reason for suggesting your calorie range - did you ask her/him the specifics?