Variety, variety, variety. For example, the Dr. Feeder challenge: In one sitting, eat

a piece of fried chicken
milkshake
cheeseburger
two chocolate truffles
fries
banana split
hot dog
slice of pizza
piece of cheesecake in one sitting.

Here's someone trying it:

They've been taking new accounts for the last 6 days or so.

I think you're right on the line--since she knows you want her fatter, she must know you're tempting her into getting fatter.

If she hasn't said anything about wanting to watch her weight or asked you not to make such fattening stuff, I think you're okay. But the day she does you have to respect that and quit tempting her or at least have a conversation about what she eats and what you cook and what your and her expectations are.

In a fatphobic society it is assumed that no one wants to be fat--if you are fat you must be weak and undisciplined. So you feel guilty when you eat a lot because you've been taught that it's a sign of weakness, of failure.

If you can transcend these social taboos and accept that you love overeating and getting fat you'll be able to get fat without guilt. But that is not always easy.

Nok said: "A thin female body, on the other hand, has (no offense) no biological reason to be attractive"

There _are_ advantages to being thin, especially in a society that has a means of storing food. A thin person is more mobile, uses up fewer resources and in some circumstances may be better able to take care of her children.

There are also advantages to being fat, especially in a society that experiences frequent food shortages. A fat person is less likely to starve to death. Fat women are much less likely to have low-birthweight babies.

So a genetic tendency to be fatter would be adaptive in some times and places, and maladaptive in others.

Since we all have ancestors from both kinds of backgrounds, we all have a mix of genetic tendencies to carry more or less weight. And we all have a mix of genetic tendencies to prefer fatter people or not. Since our own particular genetic mix will vary, even compared to siblings, we vary in our tendencies to be fatter or thinner, and we vary in our tendencies to prefer fatter or thinner partners.

Of course culture is a factor as well. For example, some societies have a tradition of eating a lot during times of food surplus so they'll survive the lean times. Some don't.

But I wouldn't dismiss genetics.

I always thought being the Fat Lady at a circus would be good for that.

If you helped them decide to gain, what was it you said or did to help them make that decision?

Was there some event (involving you or not) that decided them to start? What was it?

After they started gaining, was there some experience that confirmed they'd made the right choice?

If they're still gaining, what inspires them to continue?