Ok let's say i've finished my last meal at 5pm on Monday and break my fast on Tuesday at 5pm. Hypothetically let's say during that fed state i've consumed in the same amount of calories my body expenditures out daily, will i still lose fat? Or will i just maintain the same amount of bodyfat and weight?
You WILL lose weight. Its as simple as that. Calories in calories out would make sense only if the human body was a robot, a car or some other mechanical machine. We, however, are not, we are biological machines which have hormones that dictate what happens to out energy stores and our metabolism in response to eating or fasting.
During fasting, levels of insulin decrease in response to decreasing blood glucose concentrations, which acts as a negative feedback mechanism to prevent blood glucose from dropping any lower. This, in turn causes your Hormone Sensitive Lipase enzymes to begin to break down the triglycerides stored in your fat cells in order to use them as energy, thereby placing you in a mild state of ketosis in which your body uses fat for energy. This will cause substantial weight loss because for that entire period of time after which your body has consumed its stored glycogen reserves, it will have no choice but to utilize the lipids from the fat reserves.
Weight loss can only be achived once insulin levels drop sufficiently to allow the breakdown of fat, fasting enables this to happen very efficiently.
Calories in Calories Out proponents will probably say you will be the same weight.
I believe your body will eventually adapt to be more efficient and you will burn more calories doing the IF.
If my experience is any good for you I'd tell you that you will wind up eating less. I do 16/8 and have surely lopped off several hundred extra calories that I didn't need.
The idea of IF is not to eat less calories - if you do it that way, you have a large potential to fail, and wind up gaining weight because your body will realize it's starving and will hang on to every source of energy it can in the form of fat. It does this by downregulating your thyroid.
You need to eat the same level of calories as before, just in a shortened eating window.
This is why it's easiest to skip breakfast and shift some of the calories to a slightly larger lunch/dinner.
You also don't want to do very low carb/zero carb and IF for the same reasons.
IF does several useful and interesting things. It gives your digestive system time to repair, it lets you enter ketosis more often and adapt to burning fat/ketones, it lets you enter autophagy and burn off intra-cellular junk proteins, kill off broken mitochondira and broken cells. Think of it as a way to clean house.
How to eat enough when fasting? 4 Answers