I think the dietician is going to tell you that you are not eating enough calories. 1200 to 1600 calories is really a weight loss range, not a maintenance range for someone your age and height and activity level, and it is very doubtful you will be able to gain anything at that range. You may be able to up the calories by doing things like slipping in a bit more mayo on your sandwiches, increasing your portion sizes a little, and I agree, switching to whole milk. Another way to do it, is to eat the same way you are eating, but add a Boost shake (or 2) to your daily routine.The shakes are very healthy and will add in the calories in a nutritious way. You probably need to be around the 2000 kcal range or even more. It's good that you are going to see your nutritionist!