There’s many different ways to feel hungry as you’ll discover when you change your eating habits. It’s a very mental thing though it does have several physical triggers and effects too, kind of like being horny. I don’t think any of them are fake but just being hungry doesn’t mean you have to eat.
One thing you’ll find is that being hungry is a learned behavior. When something good happens, like eating tasty food, the brain reinforces the thought patterns surrounding it (see Pavlov’s dogs) so that in the future you have greater chance of engaging in behavior leading to the same outcome. This is how addiction works, although I’m loath to call it such except in extreme circumstances since this is one of the major mechanisms of learning and brain function. Anyway, if you happen to trigger a neutral pattern that has been linked to other patterns that get you closer and closer to eating this would also trigger hunger since hunger and eating are closely associated.
If you crave something specific, like for example chocolate, then that is your learned behavior kicking in. The brain has learned that X + eating chocolate = feels good, so if X then encourage eating chocolate. X could be anything, for example it could be low blood sugar, stress, emotions, pretty much anything. One obvious association is that thinking about tasty food makes you crave that food, because when you’re eating for example chocolate you’re also thinking about it. Determining if you should give in to the craving or not is up to you and what you figure the craving is caused by.
This learned behavior also applies to more general hunger. If you associate watching TV with eating then watching TV will make you hungry. Used to having a snack when you come home from work? Coming home is going to make you hungry. Eating makes us feel good so the brain has learned to make us hungry when we engage neural patterns that have historically been proximal to eating.
The good thing about learned behavior is that it can be unlearned when it no longer serves a purpose.
There are also signals coming from the rest of the body that make you hungry. The body periodically sends out hunger hormones throughout the day to remind your brain that it should seek out food. Without this reminder it’s entirely possible we could go for a long time without eating because we were busy doing other things, and while it’s not exactly harmful to not eat several times every day for most animals (including humans), animals that don’t spend a lot of their time seeking food typically don’t live very long. It’s a built-in biological mechanism to periodically bump food to the top of the priority list to make sure we don’t starve.
Hunger hormones could also be released outside of their usual schedule for a variety of reasons, including because the brain said to.
The bottom line what I said in the first paragraph: I don’t think there’s any type of fake hunger but just because you’re hungry doesn’t mean you have to eat. Eating is of paramount importance to survival and so evolution has given us a robust system for ensuring we seek out food, but it has also given us humans in particular a large brain with the ability to override instinctual behavior when we determine that our instincts are counter-productive.
