Back when I had an advice column I helped one woman talk to her mother about this stuff. It may help you if you end up gaining:

Dear Dr. Feeder--
My name is Amanda. Last year I began university, and because of this had to move away from home onto campus.
One thing I had promised myself to do when I moved out of home was to gain weight.
Since moving onto Campus I have just let myself go completely, and as a result gained 50lbs.
However, this summer I will be visiting my mother back home whom is very into healthy eating, and so forth.
Let me say right now that I am not loosing any weight whatsoever for her, nor do I intend to stop.
But, I do not know what to say to her to avoid her from being too upset.
What can I say to prevent her from being too angry?

Dear Amanda--
You may not be able to keep her from being angry. Settle for keeping her from nagging you to death. Try:
1. If she gets angry, DON'T get angry yourself.
2. If she asks why you gained, say it's because you like to eat and don't mind the extra weight.,
3. If she asks you why you don't diet, say you've tried diets and have found you're happier eating what you want.
4. If she makes a comment about your weight that is not in the form of a question, don't respond.
5. If she says something mean, say "Now you're just being mean."

And remember the NEVERs:
NEVER apologize for your gain;
NEVER apologize for your size;
NEVER apologize for your appetite.
NEVER promise to lose weight unless you really want to.
If she tries to get you to eat healthy food (fruit & vegetables, etc.) go ahead and eat it. It will make her feel better. You can still eat your favorite goodies as well.

If she won't shut up about it, say 'look, I know you're just saying all this because you love me and you want what's best for me, and I appreciate that, but it's my decision and you need to respect that.
Let me know how it goes!

Dear Dr. Feeder--
Sorry for the long reply period, I only flew in a couple of days ago. As you can imagine, it wasn't great at all. But surprisingly I didn't feel down about it whatsoever! When I first gave my mother a hug, she put her hand on my stomach and patted and squeezed it, constantly glancing down at it. It was horribly awkward. For some reason I expected that would be it. Later that night she gave me a brief "discussion" about my weight and asked me if anything was wrong and so forth. I explained to her exactly what you suggested, that I was happy the way I was and didn't feel the need to diet. Amazingly though, that was it!
Thankfully, she hasn't said anything else yet about my weight which I'm very pleased with. Thank-you so much for your help - the food here is quite healthy, so for that reason I'm looking forward to returning home where I can eat what I like.
Again, thank-you so much for the wonderful advice.

It's not my thing, but I'm curious why people would want to do it. A little help? I won't judge.

www.deviantart.com/cyrellexl/art/Commissions-OPEN-900080233

No hard data but: it seems to me that those who have trouble stopping are usually the same people who regularly stuff themselves to the absolute maximum, too full to take a deep breath. I mean, you can do that occasionally, but if you do it once a week or more you're apt to go out of control.

Can anyone confirm or deny this?

What I'm saying is that when you weigh all those other factors in (as you should) maybe you DON'T want to gain at all.

I said people should gain what they want, not that they can't change what they want.

You just have to gain what you want, not MORE than you want.

I would argue that even if you choose to STOP gaining at some point you've still gained what you want. Gaining what you want doesn't mean gaining without limit, it means gaining until you don't want to gain anymore. For whatever reason.

If you're not going to gain as much as you want there's no point in gaining at all.

(Just spit-balling here--comments welcome)