Obsessing over undergrad eating habits

My main job this semester is TAing a nutrition class. The main assignment for that class is a very detailed food diary assessment. I've had all sorts of interesting questions to field (my current favorite is "I ate an orange and forgot to weigh it. What do I do?????" - it was so tempting to tell the student to restart her diary the next day but I was kind and explained that she ate the evidence and could therefore make up a reasonable weight for her orange). I am currently grading the diaries. It really is like going through someone's diary. I have been so tempted to write comments like "You had HOW MANY Coors Lights?" and "No, my dear, you can not live off of nothing but Timbits" or, alternately "Is that all you ate??? That's like half your daily recommended calorie intake." I have to keep reminding myself that it is not my job. I am an impartial marker, not a physician in this situation.