Effect of IF on metabolism


(Mark Anthony Spiteri) #1

One of the arguments I keep getting from people when I tell them that I do intermittent fasting is that I will fuck up my metabolism.

I know I have heard Jason Fung say that actually the metabolic rate tends to improve but is there any science on this?

Thanks in advance!


#2

I think many people confuse IF with calorie restriction. Intentionally restricting calories can lead to a reduction in metabolic rate, as seen in the Biggest Loser results. If you are eating to satiety though, that shouldn’t be a problem.
IF helps by limiting your body’s insulin response to a small window every day, and allows better access to fat stores the rest of the day and overnight.

I’ll let someone else track down the really sciencey studies.


#3

Found a study about IF and circadian rhythm here:

@erdoke has some charts he can maybe explain regarding this.


(Carol Hawkins) #4

Hey, my first time getting to unblur words! :stuck_out_tongue_winking_eye:

I do IF daily, but eat more per meal than if the calories were spread throughout the day. That gets around the metabolism slow down due to caloric restriction


(Jane Reed) #5

If you can get hold of Dr. Fung’s fasting book he provides references, at the end of every chapter, for every claim he makes, including that of the stability of metabolism during fasting.


(Tom Seest) #6

Everyone fasts intermittently unless they are on an IV drip of constant nutrients. So, if it messes with your metabolism, it’s messing with everyone. The only thing that varies is the eating window, which for me is about 10 seconds when I’m eating.

Their logic seems flawed.


(Gabor Erdosi) #7

Having more small meals vs. fewer larger meals does not only increase the time spent in a higher insulin state, but also stimulates higher insulin load, regardless of overall identical caloric intake.

Incretin and Islet Hormone Responses to Meals of Increasing Size in Healthy Subjects
http://press.endocrine.org/doi/abs/10.1210/jc.2014-2865


(Misty Wilson) #8

Check out Jason Fungs guide to intermittent fasting! The science is there! :stuck_out_tongue_winking_eye:


(Beck) #9

I’d definitely recommend Jason Fungs book on fasting. It’s very well presented and easy to understand.


#10

An interesting way I read the explanation is this.

  1. it takes energy for the body to undergo autophagy (eating away the old parts to make room for new cell growth).
  2. if you don’t eat anything (i.e. Fasting), the body consumes it’s energy for fasting activities
  3. however, if you do eat something (like tiny snacks, every hour or so), the body consumes energy for digestion.

So, in other words, intermittent fasting forces the body to focus on ONE (or few) activities…as opposed to many. In this way, the metabolism remains strongly working on the one or few key processes.


(Angel M Chávez) #11

We are all N=1 unfortunately. I will post my experience seperately but I had my metabolism tested yesterday in lab and after a year of fasting both intermittently and extended (normal meals when eating, so not restrictive but keto) my body is in conservation mode and is 32% below normal. I will be quitting the fasting for 6 months and then testing again to see 1: how my body responds to the same caloric intake with only overnight fasting and 2: if I can fix it at all.


#12

Looking forward to seeing how different eating habits affect your results. Did you have any previous tests to compare this one to?


(Angel M Chávez) #13

Unfortunately no, but the weight gain is definitely explained with a lower RMR. I have packed on weight despite eating once per day, sufficient meals, and ketones in range.


(Roy D) #14

I’m new to this topic, so excuse me if I’m asking a question that has been answered elsewhere.

Does anyone know if there are results of metabolism rate vs length of a fast?

It is my understanding that The Fastest Loser show ran over a 90 day period, and the participant on this show experienced slower metabolisms to the point where they easily gained weight after the show ended. The show limited participants to ~800 Kcal per day plus added exercise. I can see similarities between this situation and long duration fasting. I’ve read of Jimmy Moore’s long term fasting (27 days?), and see people in this forum discussing long term fasting (greater than 7 days).

I also recall in one of Jason Fung’s books the statement that he typically recommends fasting for 3 (on alternate days) per week for his clinic patients for weight loss.

My question is; what is the trend of the reduction in a person’s metabolism vs the length of a fast?

Thx
rkd999


(sandra) #15

Would you mind keeping us posted. I have had no adverse affects I can tell but because of hearing a story or two like this I have tried to eat more meals. Long story short, I absolutely hate it and OMAD was seemingly beautiful for myself both for how I felt and saving time, etc. I did not gain after a year or have issues (that I can tell). Did you change anything else? Thank you :wink:


(sandra) #16

Did you rad it, can you offer a cliff notes? Sorry, those types of papers make me dizzy! :wink:


(sandra) #17

ya, who gets up and eats durring the night… I suppose if you are on ambien :wink:


(Dan Dan) #18

IF/EF Keto WOE is about becoming fat adapted so you don’t restrict calories :thinking:

Long EF is not normally done until you are fat adapted :open_mouth:

Good luck and much success in your journey in IF/EF Keto WOE :grin:


(Angel M Chávez) #19

Ok I finally redid my RMR and Dexa Scan after a year of eating more often. Good news is follow up is 2% above normal rather than 32% below normal. Unfortunately I also gained 11 lbs, 7lbs of fat. Starting this year out with an extended water fast so I hope I don’t thrash my metabolism again :joy: