If I tell them, they'll do two things. Help me loose the weight, or accept it and go on with life. Its quite embarrassing to tell someone you plan on losing weight, cause theres always the chance you won't. So, should I tell them? Would it change anything?

Don't tell them. That way you don't have to be embarrassed when you don't succeed. Dieting is TOUGH. I would never put my willpower on a bet. It sets you up to look like a quitter.

Maybe you should tell them on a need-to-know basis. If there is something they are serving which is fatty tell them you are trying to be healthier and can't eat it, otherwise since you are doing this for yourself there is no need to give them all the details.

Are you overweight to begin with? If you're not, then your parents could say, "You don't need a diet or lose any weight." Then what do you do?

I would tell them - it helps you to hold yourself accountable - if you know that someone is aware you're trying to lose weight, you're more likely to stick to the weight loss plan. Also they're going to notice when you start cutting back on food. Telling them ahead will stop them from worrying that something else is wrong with you.

You should tell them, because if you become obsessed about it and try stupid things like starve yourself, they will know and will advise you.

I would tell them. Things like diets work better if you have a support group. If you fail on the first attempt, you can always try again and your parents will understand. Good luck on your diet.