i see different things. some sources said that 18 hours did as much as 20 hours. if that’s the case then why do people try to fast longer? sometimes even days? what does it do?
after a certain point does your body stop burning fat?
i also saw somewhere that it’s kept to 16-18 because if you go any longer then once you eat your body will store it as it’s in starvation mode, and you’ll gain weight back
Absolutely. The longer you fast, the more time you give your body to exhaust it’s glucose stores (glycogen) and you produce more ketones in response to the low glucose levels. The ketones take your fat stores for energy because it can’t use glucose anymore, and your body stays in “fat burning” mode for longer. Also, over the course of a few days of fasting, your energy expenditure (your metabolism) actually increases because your body is producing adrenaline and cortisol to combat the stress of not eating. The body does not go in to “starvation mode” - it’s a pretty common IF myth.
I’ll also say this is generally why a keto style diet (or just low carb, high fat, moderate protein) is recommended in conjunction with IF because it keeps you in ketosis and don’t impact your insulin and glucose levels as dramatically as refined grains and sugar.
Only to the extent that a longer fast might help you eat less. The overall calories still matter. When it comes to strictly weight loss, fasting just helps to direct the deficit to burn fat by controlling insulin. Just putting the same calories into a smaller eating window won’t have a huge impact on how quickly someone loses weight.
As someone else said, it burns off glycogen.
Long fasts have added benefits. It increases insulin sensitivity (with regular prolonged fasting), increases autophagy (internal parts recycling), and staying in ketosis for long periods help a lot with endurance sports (fat adaptation in order to keep going when glycogen is gone).
Daily IF is an awesome lifestyle to get to a healthy weight and stay there. But it takes a long time. That’s okay that it does that.
Im currently experimenting with two 36 hour fasts each week on Monday and Friday (dinner day before, no food until the day after). Going to try for 48 (and if I’m feeling good- 72) this Monday/Tuesday. If you want to experiment with longer fasts head to /r/fasting. I’m sensitive to electrolyte imbalances so I need to be drinking “snake juice” throughout my fast in order to stay right.