People will never truly understand.
I just say to them my Pancreas can't produce (enough) insulin to cope with meals like ordinary folk do. So where their bodies naturally produce insulin normally throughout the day and night, we can't. (or for Type 2s, it doesn't work properly.) Without insulin, high sugars lead to a "serious situation".
That usually shuts them up. Thankfully people around me don't dictate much although they do ask questions 'can you eat that?' 'are you allowed?' And they still don't (yet) appreciate that when I near a hypo I may not be very responsive or helpful.
I just simply say I can eat whatever I want (within reason, although cakes, biscuits and choc send me very high so I avoid/minimise those) I then go on to my typical Pancreas line... :lol:
I assume you're eating a healthy diet regardless? I stick to low GI and veg protein for lunch and usually a light low GI breakfast. I then have 'normal dinner' (but with smaller potatoes, pasta, rice portions than my husband). I certainly don't feel I need to restrict myself, I should try to be HEALTHY even those without Diabetes should!
I have to keep a diary for everything as I'm newly diagnosed, but it certainly is helping me and my Diabetes team to assess, adjust and advise.
I must admit I did raise my eyebrows a few times when the Diabetes nurse was talking about 'when you have a Mars Bar...' and I thought I've not eaten a full bar of any chocolate in years! I think they're just trying to make you feel normal rather than restricting or dictating to you what to eat especially if you're young.
They know we've got hassle enough with managing the Diabetes so I think they mean well. Obviously they should not be advocating an unhealthy diet.
Maybe you should take your BF along to your appointments? I've taken my sister and my husband along and neither have told me what to eat.
Good luck and rant away here with us!