I'm going to be rude to my doctor.
Why do you want to be rude to your doctor?
They told me to follow a very strict diet.
Although it's not always easy following a strict diet, you should take the advice of your doctor. There's no reason to be rude to someone who is trying to help you since it will just annoy them and make them less likely to help you in the future.
It is just too hard.
Have you tried talking with them to learn how to cope with the strictness? If it is emergency weight loss you really need to stick to it for your health.