Gastric Bypass Surgery Support Group
Gastric bypass (GBP) is any of a group of similar operative procedures used to treat morbid obesity, a condition which arises from severe accumulation of excess weight in the form of fatty tissue, and the health problems ("co-morbidities") which result. If you are considering gastric bypass or have had it, join the community where we share our experiences and find support.

If you aren't keeping a food diary, start doing so right away because that is how you know how much you are eating. For me, I had to eat no more than 1,000 calories a day for weight to come off. To do that, I cut carbs without increasing calories. It's what I still do when I need to drop a couple of pounds to maintain.
I lost too much weight initially, and found I was having several episodes of low blood sugar a day. That was really scary. My surgeon told me to gain 10 - 12 pounds, which put me at the weight he had initially told me was my goal weight. Sigh. He was right, shooting for my high school weight was not realistic or healthy for me.
As to quantity. I find that the bulk contained in a one cup measuring cup is the MOST I can handle. I'm really more comfortable at a smaller bulk as far as solid foods go. The important thing is to become aware of the "soft cues" your body gives you to indicate that it is full. You need to learn this new body awareness, because after GBS, you no longer get traditional "full" signals.
So, some soft cues are:
a gurgle in your gut on the lower left side where your pouch empties into the intestine.
a sign
a runny nose
a sneeze
a hiccup
a burp
I'm sure there are more because we all seem to have our own unique soft cues. Maybe I'll start a discussion thread.... that will give you a good list.
Hope this helps. :)