Question about BMR when doing 24-hour fasts

Hi Everyone, After read both of Dr. Fung's books on fasting/obesity and buying his cookbook, I have been fasting for about 20-24 hours a day for the past 2 weeks. I'm liking it a lot. I have one question about BMR. Dr. Fung talks a lot about America's Greatest Loser the show and how the contestant's BMR goes down over time because they are eating at a deficiency. On most OMAD days, I struggle to eat my calorie needs and is usually at a deficiency. This has been great for weight loss but I was hoping to keep my BMR up as well. My thought on this, after reading his books, is that since you are reducing your insulin spike to one time a day, your body will use the body fat to take in the remainder of the calories needed to maintain a higher BMR. So my question is, does eating less during OMAD reduce BMR? Is this why he suggests alternating fasting days to keep BMR high? And lastly, for people doing OMAD, do you normally get in your maintenance calories in one meal? Video where the information came from: https://www.youtube.com/watch?v=ETkwZIi3R7w&t=1762s Thank You Very Much!

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My understanding is that a chronic state of deprivation can lead to a lower BMR. If you eat at a calorie deficit and spread those calories over the course of a long day, never allowing your body to fully get into fasting mode when you are not eating, then I think your brain would interpret that as chronic deprivation. If you are eating OMAD style and feeling full when you are done, I think your body would interpret that as a state of abundance..and when you are fasting, you would be tapping into a different, presumably abundant nutrient source, body fat. So once again, no deprivation signal. I don’t count calories with OMAD, but I guess I do embrace incorporating a lot of healthy fats into meals, so I imagine my calorie count is on the higher side because of that.

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From what i understand, when you eat until satiated the stomach (or hormones?) tell your brain that food is a plenty and not to lower BMR. When you eat and stop because you have eaten your daily calories and are not satiated, body lowers BMR because it thinks there is not enough food around. This is a simple explaination from what Ive gathered.

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This is very reassuring. I’ve been doing pretty strict keto OMAD and having trouble eating more than 1000 calories a day. I’m very full and find it quite easy to fast for 22+ hrs a day. Thanks for the info.

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Well the people on biggest loser do basically micro meals of processed junk all day and 8 or more hours a day of very high intensity workouts. It’s not uncommon for them to spend several hours a day running on the treadmill. Then hiit, then more running, then a processed meal while because massaged and examined by doctors, then repeat twice. The type of deficit they have daily is huge, matched with the insane stress levels they have. You would have a hard time matching either of those levels.

As long as you are still working out, still lifting weights, hydrating and maintaining your stress levels your BMR should increase.

But. Fung also talks about plateaus and having to extend our fasting periods after awhile to get the same results. Later in your journey you may need to switch to 48’s until you reach your maintenance weight.