If you already made an apointment with a dietitian, you know that for consultation you need a 5-day or at least 3-day food record. Writing the food record should be as detailed as possible (serving portion sizes, content of fat, kind of product etc.). It is the only way how dietitian can get to know your nutritional status. Dietitian also needs to know your eating habits, body composition and physical activity.
Writing a food record can help you to realize how much you actually eat or vice versa. Try to write a food record for a few days.