Can someone clear up some stuff for me re: fasting & calorie deficit?

Despite having done so much research into intermittent fasting and calorie restriction, I’m still super unclear on some of the mechanisms of the two: i If the role of intermittent fasting in fat loss is to lower insulin so that the body switches over to “fat burning mode” then isn’t a calorie deficit still king? Before entering fasting mode, doesn’t your body first have to burn off any calories consumed? On that note, would eating the same number of calories over an eating window of 6 hours have the same results as eating over 16 hours? If not, why? ii I recently found an article about how our body can only burn a certain number of fat calories a day before switching over to muscle, based on the amount of fat we have on our body. For me, with a body fat percentage of roughly 21%, supposedly my body can only burn 950 calories from fat a day before starting to switch over to muscle mass. In that case, would time restricted eating be more effective for fat loss than alternate day fasting, as during the fasting days, of the 2000 calories I would burn (as per my tdee) only 950 would come from fat? Vs say a daily caloric deficit of 950 calories? Any info is much appreciated!

Answer

It is tied to (food) glycemic index you are taking in - not to calories - and the resulting weight loss is by ketosis. I won’t post the definitions here but the idea is your body uses its own fat converted into ketones as its energy source, instead of using blood sugar - glucose - carbs.

Answer

Being in a caloric deficit will mean that you will be consuming less than or possibly less than your body metabolic rate, base metabolic rate whichever its called. If you arent consuming the minimum calories per day then you would have a more difficult time sustaining yourself even within your eating window. For a caloric deficit, id reccomend cutting it back a hundred calories to start and not so much balls to the wall 50% of what you would normally consume. That could put strain on your body and you may experience fatigue not from fasting but from not taking in enough energy. Dont want to burn yourself out at the beginning.

Once you fast beyond 16 hours then the body will begin to do this thing called gluconeogenisis and create glucose from energy stores in the liver and converting body fat to energy. The longer you fast, the better is what is usually explained here and there.

To keep it simple, i would reccomend eating maintenance calories and start with a 16 hour fast to start things off. I did a 16 hour fast my first day last two Thursdays ago but after my first 16 hour fast I changed it to 18 hour fasting a 6 hour eating to match it to my work lunch schedule and have kept it at 18 hours fasting and even did my first 20 hour fast today and it was almost a breeze.

I did 8pm to 12pm the following day fasting and then ate between 12pm to 8pm, mindfully of course and I used the myfitnesspal website and app to create and log my meals for the day.

Staying hydrated also helps bigtime to control hunger, often times hunger and thirst get confused. Hope you find your way. All this is just opinion and experiences from my IF journey.