Nighteyes post_id=5168 time=1511778420 user_id=93 said:
I am struggling with understanding the precise difference between calorie restriction and intermittent fasting. When you do intermittent fasting such as eating once per day or something (like Jason Fung from the videos claims he does), how do you not end up eating less calories?
Is the main difference the time between intake of calories so that even though you decrease calories when doing intermittent fasting your baseline metabolism doesn't decrease because insulin goes down? Or what is it that makes sure your baseline metabolism does not decrease on intermittent fasting vs caloric restriction?
I find it really hard to keep calories high (above 1500 kcal) when eating just one meal a day. I still get cold hands sometimes but I compensate with more exercise and sauna which helps me sweat and keep temperature up. I just want to understand why IF would not lower basal metabolic rate like Jason Fung claims.. maybe I am missing a key link here. @mattyb do you think you could help me understand this?
Jason Fung talks out of his ass a lot of the time. No evidence IF doesn't lower BMR. Anything that causes weight loss will lower BMR, because BMR is ultimately a function of systemic metabolism, and the more tissues you have the higher the systemic metabolism. It may not lower BMR as much per unit of lean body mass tissue, but again, it lacks evidence for that.
IF can mess with the measurements of BMR if taken too late in the day, because it increases adrenergic response, which covers true resting metabolic rate. I have seen this happen in myself. I had to fast until 4PM one day for a BMR test when I was in school, my resting BMR was +500kcal above predicted and I was wired and jittery at the time. That's because BMR tests are supposed to be taken in the early morning, when you get a true view of metabolism.
If you don't have fat to lose, but still want to try out IF, just make a bigger eating window. One meal a day is ridiculously hard, I have tried it many times - you will lose weight with that. Try three meals a day inside an 8 hour eating window. Much easier to maintain weight with that.