Today I tried intermittent fasting for the first time. I wanted to go for a walk and run without food digesting, so I essentially fasted from 8pm the night before to 4pm today. Then I got home and had a pound of wild-caught fish over oily greens, which usually would satisfy me for hours. But today, it just didn't, though possibly it was because the meal didn't have quite enough fat or black pepper. I found myself grazing the rest of the day and eating more greens with baba ganoush. Overall, it's still probably a little less, in calories and protien, than I might have eaten if I hadn't fasted today. But it seems like I somewhat made up for the fasting by eating more than I usually do in the evening. Now I'm totally confused if the the goal of IF is to eat less food overall by retraining hunger or to just create longer breaks between food, to allow the body to focus on other mechanisms?
It's controversial. Some argue that it is the time fasted that confers the benefit, and others argue that it only works because of the induced caloric restriction. This paper says it's independent. Studying these arguments is on my to-do list, so I don't have an answer, but I offer up at least some evidence that might help you decide.
I've had this effect me both ways.
The point of IFing isn't to alter calorie intake, since ex hypothesi you should be getting the benefits just from a reduced eating window (less post-prandial stress) and more time fasting for your body to repair without the stress of digestion. So there's no need to worry if you are eating precisely the same amount, since the benefits should come from other factors. There's no need to worry that you "made up for the fasting by eating ... [a little less than if I hadn't fasted today]." IFing isn't necessarily about calorie restriction. There's no trick you can pull to allow yourself to restrict calories (below needs) indefinitely, since by definition, indefinite calorie restriction is unsustainable; IFing conversely, is a healthy way to consume your daily calorie intake indefinitely (potentially).
It would be quite plausible, however, if you were to want to eat less while IFing, since a) you should be burning more fat during the fast and so should need to consume less, b) you'll be avoiding the swings of post-prandial hunger, when your digestive system is primed to consume things and when you've got elevated/depressed blood sugar and elevated triglycerides all increasing appetite.
As to whether IFing might result in increase hunger overall. Well, it might sometimes, certainly it's seemed to for me on occasion. But it's quite plausible in either of our cases that it just seems like hunger's increasing, because eating two days of food all at once seems a lot more. Since you say that you ate "probably a little less, in calories and protien, than I might have eaten if I hadn't fasted today" there doesn't seem to be anything to worry about. It's not implausible that fasting (especially if you're new to it) might cause your body to want to eat more than usual just to be on the safe side (or that this might be a purely psychological effect in some people, as a consequence of consciously not eating for a lengthy period, or because it takes longer to sate the increased amount of hunger, which indirectly causes you to eat past the point of satiation). Even were this so though, it would be premature to judge this to be a problem on the basis of an isolated post-fast meal. In theory, you would expect to subsequently eat less at the next meal, due to the natural action of leptin decreasing your appetite commensurately. IFing and so reducing your triglycerides etc, ought only to aid this process. Indeed, this sort of pattern (increasingly infrequent, larger meals) seems to be what a lot of paleo people are ideally pursuing with their IFing, on the basis that it seems an intuitive hunter-gatherer pattern.
If you're trying to lose weight, then IF can be both a way to restrict calories without letting your body adjust to a day-to-day caloric limit by curbing your metabolism, and a way to learn the difference between mouth hunger and real hunger.
I have the same response as you - if I have fasted, then I can eat so much that my gut is swollen and sore, and my brain still doesn't register that it has had enough to eat. I deal with this by dinner-to-dinner fasting & a 'no eating after 7:30pm' rule, along with copious amounts of tea and water.
You should be eating a normal-sized, highly nutritious meal to break an IF, not eating more to compensate.
However, if you are fasting for other reasons, then you might want to eat a bigger meal (feasting) at the end of the fast, to model the eating patterns of traditional tribes. I've read that if you're getting a lot of activity within the fasting period, you do want to eat quite a bit at the end to maximise muscle development and recovery.