Fasting has been around since the dawn of time and is one of the most natural things that we can do. Why is that?
Food was not always readily available during our evolution on the planet. It is only quite recently that we have food at our fingertips in our society for the vast majority of us. Since we went through periods where food was very scarce regularly, like during winter, one could make the argument that our bodies are designed to fast.
"But I feel hungry and my stomach is growling!"
This is to be expected since your body has been conditioned through habit to expect food at a certain time. What you are feeling are your hunger hormones and carbohydrate cravings. Does this mean that you are starving? Likely not. True starvation is when your body is running very low on micronutrients such as vitamins, and macronutrients like fat and protein. During a fast, you have no exogenous (external) calories coming into the body, so the body has no choice but to start using its endogenous (internal) calories, which is stored body fat.
The human body is the master of adaptation. Any stimulus that affects the body, especially if done so regularly, the body will adapt and try to achieve balance as quickly as possible. The adaptations that have occurred due to the stimulus will make the next time a bit easier. This concept is called hormesis. For example, when you do resistance training, you are breaking down and tearing muscle tissue. Literally. What is the adaptation? You get bigger muscles so that you can handle the weight load better the next time. When you practice cold exposure (like ice baths), your body creates more "brown fat" and the "beiging of white fat" occurs. This is due to more mitochondria (the energy centers of our cells) being sprouted to facilitate faster and more robust energy production. The benefits of these positive adaptations are extremely valuable and will affect us in many ways and many areas of our lives.
Fasting is one of those positive stressors that have a profoundly positive impact on our longevity and how effectively we absorb the foods that we are consuming.
If the body has been conditioned to predominantly expect carbohydrates as a fuel source, its ability to burn fat compared to someone following a low-carb (ketogenic) diet is greatly impeded. It is possible to get "fat-adapted" or "metabolically flexible", meaning your body can use both fats and carbohydrates optimally. One thing that needs to be mentioned is that people following a low-carb (ketogenic diet) long-term develop physiological insulin resistance. This however is not the same as pathological insulin resistance in the case of someone who is pre-diabetic or a type 2 diabetic. As with everything, it comes down to balance. There are no problems cycling in and out of ketosis (cyclical ketogenic diet), but it might be a mistake to think that carbohydrates are the enemy. Carbohydrates may exacerbate a problem like pathological insulin resistance, but it does not mean that it caused the problem in the first place.
Quality of fats - you are what you eat.
Since you are going to start utilizing your own body fat for intermittent fasting, you would only want to include the best fats in your diet. Remember, we are mono-gastric animals (we have only one stomach), so whatever fat we eat, we are going to store it in the same form as it was when consumed. Ruminants like cows and sheep have multiple stomachs and can convert dietary polyunsaturated fats which they get from vegetables and grass to saturated fat (their stored body fat). Why is that important? Polyunsaturated fats are very susceptible to oxidation which is a process that we don't want since the fats go rancid. Consuming these types of fats can be very inflammatory and can cause a range of health problems. You do not want your body fat to be enriched with these unstable fats! How do we avoid these fats? Eating more stable (saturated fat) from good sources like coconut oil or animal fat (if the animal is healthy and eating a species-appropriate diet, the fat is healthy) would be your best bet. The main culprits to exclude from your diet immediately are hydrogenated fats and omega-6 rich fats like linoleic acid. These are oils like sunflower oil, safflower oil, soybean oil, rapeseed oil, canola oil, and margarine to name only a few. The golden rule is to stay away from ultra-processed foods. In the case of fats, if the fats can be extracted by mechanical means, such as a cold press from whole food sources like coconuts or olives, it will be among the safest to consume. If they have to do a chemical extraction and hydrogenation, it is very dangerous and hazardous to human health.
Here is a video of a holistic doctor, who is also a former Olympic decathlete explaining fasting in a comprehensible manner
What can help you on your intermittent fasting journey?
Having an app to keep track of your fasting window and helps to track your weight is very valuable. There are many free apps like this available to us on our phones and maybe a good idea to utilize them until a proper routine is established that feels natural and works well for you.
In closing, fasting is one of the most powerful interventions that can be done and will certainly improve our general quality of life when done correctly.