Back before Costco, Lean Pockets, and Pepsi I'm sure the relationship between energy levels and hunger was a bit more straight forward.
Hunger is caused by a peptide (cousins of a hormone) called ghrelin. A lot of things can cause this to rise and fall, including sleep schedules. Most people notice that on days where they get poor sleep, the next day they will be much hungrier and make bad food choices. That obviously has nothing to do with the energy reserves you started the day with, and if food really stopped hunger in the short term then simply eating a big breakfast would stop the cycle.
What is the relation of hunger and energy?
It's very intricate. For most people, feeling hungry is because of insulin spikes:
...that elevations in insulin produce increased hunger, heightened
perceived pleasantness of sweet taste, and increased food intake.
It's a bit of a viscous cycle because eating simple carbohydrates (bread, rice, sugar, flour, etc) produces insulin which makes the food taste better and makes you hungrier. Insulin is also an anabolic hormone that provides for fat storage.
If we fool hunger by eating LEDF does this not stop having the energy
need for body ?
No. You most likely have far more energy than your body needs to get through the day and possibly through the next month or two, just in fat and sugar (and to a lesser extend muscle) reserves.
If you were a 4% body fat hunter gatherer living 300K years ago then yes, you really would want to ensure that you're sucking down every calorie you can get your hands on and never want to pass up a meal. Unfortunately, we share the same biology of our ancestors and food marketing companies know how to work with this.
Isn't hunger is the natural signal for energy requirement ?
Not for the vast majority of humans in the developed world. As shown above, hunger can exist because you ate too much bread or didn't get enough sleep. I don't know if there is any data on it, but I would venture to guess that the average westerner might never have had hunger caused by anything other than spurious signals, most of which are engineered by food companies.
If you get a chance, I'd recommend watching (and sharing) the movie Food, Inc.