How much should one eat when following the not-eating-after-noon precept?

In my understanding, there are a few ways to follow the not-eating-after-noon precept. Here are what I know of: 1. Two meals per day + juice/sugar water: breakfast and lunch, juice or sugar water for dinner. 2. Two meals per day: breakfast and lunch, nothing but plain water after noon. 3. One meal per day: lunch only. Plain water only before and after lunch. I am a layperson working in an air-conditioned office. In my experience of method 1, I can do with normal amount of breakfast and lunch. But for method 2, sometimes I need more amount of lunch, say 1.5 times of a normal lunch. Never did try method 3. I wish those who have experience can share their thought on the appropriate amount of food, and also the ways of following it. I believe Buddha had suggested to have moderate amount of food, but how much is considered as moderate?