Because we don't enter the fasted state until 12 hours after our last meal, it's rare that our bodies are in this fat burning state. This is one of the reasons why many people who start intermittent fasting will lose fat without changing what they eat, how much they eat, or how often they exercise. Fasting puts your body in a fat burning state that you rarely make it to during a normal eating schedule.
While these five methods are the most well-known in terms of integrating periods of fasting into your eating schedule, there are many other similar philosophies based on meal timing. For those who prefer a more fluid, less rigid method, there’s also the concept of eating intuitively. Primal Diet proponent Mark Sisson is a supporter of the Eat WHEN (When Hunger Ensues Naturally) method, where dieters simply eat whenever their bodies ask them to. However, some believe this can also lead to overeating or overconsumption of calories, since our bodies’ hunger-induced choices may be more caloric than otherwise.
A 2018 review of intermittent fasting in obese people showed that reducing calorie intake one to six days per week over at least 12 weeks was effective for reducing body weight on an average of 7 kilograms (15 lb); the results were not different from a simple calorie restricted diet, and the clinical trials reviewed were run mostly on middle-aged women from the US and the UK, limiting interpretation of the results.[25] Intermittent fasting has not been studied in children, the elderly, or underweight people, and could be harmful in these populations.[25][26]

Intermittent fasting (intermittent energy restriction or intermittent calorie restriction) is an umbrella term for various eating diet plans that cycle between a period of fasting and non-fasting over a defined period. Intermittent fasting is under preliminary research to assess if it can produce weight loss comparable to long-term calorie restriction.[1][2][3][4][5]
So, the idea that intermittent fasting is bad for women is only partially true. Your body will do strange things if it thinks it’s starving. That’s normal, expected, and part of your evolutionary biology. The key to making it work is to give your brain the energy it needs and assuring your metabolism that everything is a-o-k and you’re not in the middle of a famine or disaster.
Every study seems to support cognitive and health benefits for IF. Studies are coming out showing it may help stave off heart disease and it’s even been shown to halt or possibly reverse brain-related diseases such as Alzheimer’s. If in doubt, check out Jason Fung’s youtube videos along with a couple of youtube researchers who do wonderful analytics, an American who lives in Japan who goes by, “Things I’ve Learned” and Thomas DeLauer’s IF material. I’ve been doing IF myself for a few months now and I feel better, more energy, better sleep, and controlled weight.

If you're looking to lose weight, this isn't a problem. And even if you're happy with your weight, this won't prove to be too much of an issue if you follow the daily fasting or weekly fasting schedules. However, if you're fasting for 24 hours per day on multiple days per week, then it's going to be very difficult to eat enough of your feast days to make up for that.

Intermittent fasting is using the same reasoning – instead of using the fats we are eating to gain energy, we are using our stored fat. That being said, you might think it’s great – you can just fast and lose more weight. You have to take into account that later on, you will need to eat extra fat in order to hit your daily macros (the most important thing). If you’re overeating on fats here, you will store the excess.
The five most common methods of intermittent fasting try to take advantage of each of these benefits. But different methods will yield better results for different people. “If you’re going to force yourself to follow a certain method, it’s not going to work,” says trainer and fitness expert Nia Shanks. “Choose a method that makes your life easier,” she says. Otherwise, it’s not sustainable and the benefits of your fasting may be short-lived.
As a lifestyle-leaning research doctor, I needed to understand the science. The Obesity Code seemed the most evidence-based summary resource, and I loved it. Fung successfully combines plenty of research, his clinical experience, and sensible nutrition advice, and also addresses the socioeconomic forces conspiring to make us fat. He is very clear that we should eat more fruits and veggies, fiber, healthy protein, and fats, and avoid sugar, refined grains, processed foods, and for God’s sake, stop snacking. Check, check, check, I agree. The only part that was still questionable in my mind was the intermittent fasting part.
There is a reason that you crave fatty and salty foods when you’re stressed – adrenal exhaustion. Listening to your body, then eating something soaked in grass-fed butter and coated with high-quality salt gives your adrenal glands what they need. Higher overall fat intake combined with a sprinkle of pink Himalayan salt can do wonders for adrenal function.
Following what Greg lays out for us, we should wait a couple of hours and stave off our cup of jolt, kick-starter for at least a couple of hours after getting up. Instead, we should have some hydrating water. That’s a hard one, let’s be truthful. Real hard, especially for coffee lovers, but I suppose there is a reason for this. I think this has something to do with cortisol levels. This really helps when, or if you get hunger pains and then have a cup of wakey juice or two or three or four cups. This almost always alleviates the hunger, so this is why it’s so powerful.
When you eat a meal, your body spends a few hours processing that food, burning what it can from what you just consumed.  Because it has all of this readily-available, easy to burn energy (thanks to the food you ate), your body will choose to use that as energy rather than the fat you have stored.  This is especially true if you just consumed carbohydrates/sugar, as your body prefers to burn sugar as energy before any other source.