But if in fact you are just trying to set a healthly life style for yourself, then you need to sit down with your dad and have an honest and open talk with him. And tell him how it makes you feel when he dows things like that.

Going cold turkey off of junk food will only lead you to the path of failure. When you cut out things your body is used to having, your body goes into a rebellion mode and wants what it wants. So, your best defense is this.

Learn self control, it will help you not only in your eating habits but will also be benenficial in every aspect of your life.

By the way, it is not rude to not accept an offering of food or anything else. if you don’t care for it, you owe no one an explanation, just a mere "No Thank You", is sufficient. Then let it go.

If there seems to be an awkward silence or and insitance to take the offering, you can eith restate you previous answer, or ignor the insistance and change the subject.

You did mention that everybody else in the house can be on a diet, and I’m wondering if this could be an underlying problem.
Why is everyone on a diet? Why is it so important to everyone? Just because everyone else is on a diet, do you really need to be on one also?

There are alot of factors to add here, but most of all, be true to yourself. You know what you want for yourself, and eating healthier for your future is admirable, and I hope you stick to it.

Good luck Jackie