Wrong
Proven by who ?, can show you even on here many people fast and lose weight, not to mention countless elsewhere.
Even if you use the old cals in v cals out way of thinking, its simply impossible to gain weight if your not eating\abstaining or consuming less than your body needs.
Whole reason we have fat stores is for energy and for our body to use it, why wouldn't you body used stored energy if its there ? If your constantly eating your body will have no reason to use the glucose in your blood and then your fat stores for energy, it would just use the food your constantly eating. Remember 1 pound of fat is about 3000 calories, we are carrying more than enough energy on our bodies.
Only when you have no fat stores, your body will turn to muscle and then you will die as you have no energy source.
You only go into "starvation mode" when you have no fat or muscle left on your body, your body will also use excess skin as its mainly protein hence why you have never seen a POW or holocaust member with loose skin, as their body will use it as source of energy
With your logic our body thinks we are dying when we are sleeping
Also there millions upon millions throughout human history would have died from fasting, but that simply isnt the case. Throughout human history eating all day everyday wasn't the norm, feast and famine spring to mind.
Aint no surprise there are so many fat unhealthy obese people in the world who are eating, which correlates with the "recommended" daily diet These are issues we never had prior to recent times, now its almost an epidemic in the western world.