I stopped going into the exam room with my children when they were in their mid-teens. I would have a conversation with the doctor after the visit, but it is important for teens and young adults to know that they can have frank, honest discussions with their doctors and have their medical privacy respected. Very few teens are going to discuss their sexual health or their alcohol and drug use with a doctor if mom is in the room. It is also important for teens and young adults to take ownership of their own health and medical relationships, and that doesn’t happen when parents are present.
I feel that by the time they have graduated from high school, most teens are better served by a GP or internist rather than a pediatrician. It’s hard to discuss adult health issues in an exam room decorated with teddy bears. A pediatrician is not an expert in adult weight issues (or adult health issues in general). While most pediatricians will continue to see their college aged patients, this is a good time to transition to a “grown up” doctor.
A 19 year old is very aware of having gained weight, and certainly doesn’t need it pointed out by parents. Unless she lives in a cave, she is also aware of the relationship between eating habits, exercise and weight gain. The best thing to do is model healthy behavior without saying a word. Don’t comment on what she looks like or what she eats.