Comments on: Part 6: What Happens To Your Body When You Fast? – Q&A

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Foods That Kill – Part 3 of 6 | Vegan Vegetarian — Wed, 25 Jan 2012 23:22:48 +0000

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[...] What happens to your body when you fast? [...]

By: Mike OD

Mike OD — Tue, 17 Aug 2010 23:19:20 +0000

Exercise is also a key to keep the metabolism strong, especially intense training like intervals and weight training (even if only a couple times a week). If you are taking any hormonal based meds, yes that will completely change things (as hormones rule the body when it comes to weight gain and loss). The faster you lose weight, the quicker it can rebound back too (as the body remembers that set point). Avoiding foods like breads/pasta and dairy may help also lower that set point.

By: miracle

miracle — Tue, 17 Aug 2010 16:03:41 +0000

i have been doing 12 to 15 hour fast daily and lost weight. When i cheat i gain twice as much back. Now it’s hard for me to trick my body into burning fat while fasting. how can i jump start my body into burning fat while fasting daily.

If I have to do a full few days of fasting, what shall i do when I break the fast? Would my body immediately start storing my food thus ‘HERE COMES THE WEIGHT GAIN.
How much weight can you lose by doing a 3 day water fast?

also, by taking steiods thorw off the whole fasting prosess?

By: Martin Berkhan

Martin Berkhan — Wed, 18 Nov 2009 00:58:29 +0000

No problem, Scott.

Rodent studies on metabolism/nutrition are often used as an example to what occurs to humans under similar circumstances, but we’re actually quite different in some instances.

By: skustes

skustes — Wed, 18 Nov 2009 00:44:55 +0000

Hey Martin,
Had a chance to actually read through what put up there. I remember when I wrote this a little over a year ago that you wrote me asking for the source and I pointed out that it was a rat study. Looks like I forgot to go back and change the post.

Thanks for clarifying a couple things. I’m going to update the series where applicable and give you credit.

Cheers
Scott

By: skustes

skustes — Tue, 17 Nov 2009 15:48:29 +0000

Thanks for the info Martin.

Cheers
Scott

By: Martin Berkhan

Martin Berkhan — Tue, 17 Nov 2009 05:56:08 +0000

Just a few short comments on some claims here. Sorry if this has been covered somewhere among the comments, I haven’t read through them all.

“Liver glycogen levels are depleted within 8-10 hours. Muscle glycogen falls by 50% over 24-hours, even without exercise. ”

False on both accounts. Liver glycogen is completely depleted in approx 28 hrs (Cahill et al). And the second statement is also incorrect. In humans, muscle glycogen is barely affected at all after 24 hrs, assuming no strenous activity.

“After depleting glycogen, amino acids are recycled to be broken down for glycogen through gluconeogenesis. ”

This is an ongoing process, but liver glycogen does not need to be depleted in order for amino acids to contribute to the maintenance of blood glucose. The longer the fast, the greater the contribution – for example, after 16 hrs, aminos will start contributing more than 50% to the amount of glucose in your blood stream. After 24-28 hrs, 100%.

“We see increases in three of the four hormones driving lipolysis, indicating a propensity towards fat burning. Somewhere around 12-18 hours, lipolysis becomes a major energy pathway, producing energy from body fat. ”

Yes. In fact, after an overnight fast, 2/3 of the energy burnt are free fatty acids. Eat breakfast and you’ll be putting the brakes on this process, of course.

“T3 levels fall slightly, indicating a slightly lower metabolic rate. Urinary nitrogen excretion falls, indicating less catabolism of muscle proteins. ”

No. Are you looking at rats now again? Because the downregulation of T3 takes more than 72 hrs to occur ih humans. A short fast in the 16-24 hr range certainly doesn’t impact negatively.

By: Mike OD

Mike OD — Thu, 12 Nov 2009 17:42:17 +0000

@Mary – Think of it this way….you fast everytime you go to sleep and wake up. Don’t sweat over it too much. It’s more important to make sure you are eating healthy and enough calories (without going into a starvation mode). Not about starving yourself afterall, just getting some deficit and burning fat.

By: mary

mary — Thu, 12 Nov 2009 03:54:40 +0000

Thanks Mike,

I have a new question about IF– If I am doing two 18-24 hours fasts a week what would you think the non fasting days would be like? I find I’m still not eating for a certain period of time like 12 or 14 or 16 hours. Is that bad? Is that chronic fasting? I don’t want to negate to good things IF can do for me.

I did download the free book thanks!