16/8 versus 15/9 IF?

#1

I know, results may vary, but I am wondering if there is something magical about that 16 hours of fasting that is always discussed? In other words, is 15/9 just about as effective for weight loss or is there something scientific or some valid reason why that extra hour really benefits?

The reason I ask is because I am pretty much doing 15/9 IF every day. Due to our lifestyle and schedules we eat late in this house, so I skip breakfast and don’t eat lunch until 1:00 or so. This works out to 15 hours. Do I need to up my effort to either get dinner an hour earlier or make lunch an hour later, or is 15/9 “close enough”? I’m losing weight but wonder if I would be losing faster with one more critical hour.
Sue

(Roy D) #2

I’m not sure if it really matters. A key to the Keto diet is the control of insulin levels. A major impact to insulin levels is if a person has Insulin Resistance (IR). Both a person’s insulin level, and level if IR varies from person to person. To someone with a high IR level, the longer fast may be more beneficial, but to someone with a low (or a non-elevated) IR level, it matters less. So I would think that difference between 15/9 and 16/8 in your case may not be significant.

If you are getting results, you’re doing good job.

(Roy D) #3

Also, Dr Jason Fung in “The Obesity Code” book recommends alternate day fasting for patients he is working with for weight loss. But a beauty of the Keto diet is that it is flexible, and if it is working for you with 15/9, and it fits your lifestyle, it seems there is no major reason to change.

JMO

(Mel Soule) #4

@Susan777 I don’t think it really matters either. 15/9 is fasted 63% of the time and fed 37%. 16/8 is 70%/30%. IMHO the earlier I close the eating window before sleep and the better I time my exercise window to occur during the last 2 hours of fasting matters more.

FWIW I am coaching some new folks right now and calling IF flexible fasting. (I’ve never like the term intermittent fasting because to civilians it can be confusing and flexible sounds better and they feel in charge. Intermittent sounds like a prescription. And it screws up the melodious sound of the FF alliteration…LOL)

They sleep 8 hours and I’m asking them to expand their sleeping/fasting window. Week 1 they stop eating 1 hour before bed and wait 1 hour after waking to eat. Week 2, 2 more hours before bed. Week 3 1 hour later eating after waking up. By end of week 3 they are 13/11. Week 4 they should be 15/9 or 16/8. Three have done it effortlessly. 1 got to 16/8 by herself at end of week two. Interested to see how the other 2 have done this week.

BTW they are not eating keto. I told them to eat whatever they wanted, which most people will do anyway starting out. So no rules on diet, just honor your fasting time. One will have separation anxiety with Ben & Jerrys and is the only one reporting hunger problems extending the fasting window. The other two don’t seem to have cravings. We have starting weights and tape measurements. I have not asked for any repeat measurements yet. They message me without asking with early scale and tape victories. Original plan was a 30 day weight and tape series. Coming up on that soon. I’m getting very excited for them.

These are not strangers to me. I have been an executive coach for several years and these guys/gals, my clients, run/own companies so there is already a level of trust that I’m constructing this upon.

#5

Actually, regarding the term “fasting”, I don’t consider the way I eat to be fasting at all. Instead, it’s more like simply eating twice a day with a 15 hour gap in between. It’s become such a way of life I think it would become an effort to eat more often, and God knows if I get back into the habit of grazing and snacking, I’ll be right back where I started. I love not being hungry!!!

#6

Way to go on being such an excellent and successful coach! Obviously you’ve earned the trust you’ve developed and I’m sure it’s rewarding for both coach students.

#7

As far as the major difference, I can’t see that extra hour mattering a whole lot. I’ve read a few times that the maximum detox benefits of a shorter fast occur between hours 18-24 but who knows how scientific that is? 15/9 for a daily IF is still pretty good.

#8

From my readings I have the impression that a smaller eating window the better, that around hour 18 is when autophagy starts to increase (though some say hour 21 or longer), and that randomness is important to keep the body responsive and to avoid ruts (such as 4 days with more fasting, 3 days with more feasting, etc).

However, it’s supposed to be a natural process - not a forced one that feels too unpleasant.

One trick for my expanding the time of fasting was to use a cup of tea, bouillon, or glass of mineral water w/lemon to see if it would settle me enough to delay eating further. And it sure did - to the point that a few times I’ve gone a full 24 hours while immersed in projects/work without any deprivation! However if such drinks don’t help us prolong the fast - then imho we’re not ready for it physiologically and/or psychologically. Increased satiation for longer periods of time varies with metabolic states and mental states/stress levels/cortisol!

The great thing about shorter eating windows (whether 9,8,7,6,5,4 etc) is that it does help improve enzyme levels over time, and is a great change away from the mindless grazing and S.A.D. anxiety hunger thing.

Be kind to yourself!

(Pete A) #9

I’ve been doing 15/9 throughout my 5 months Keto, not at all because I set out to fast, but because I happen to eat dinner at 6:30-7:00 and breakfast at 9:30-10.

I’ve considered trying 16/8 because of all I’ve read on this site, but haven’t read anything persuasive enough to change it up. Although I’m open to change if I knew there’d be a benefit.

I’ve wondered about this @Susan777 so thanks for asking!

(Mel Soule) #10

@Susan777 Exactly. Could not agree with you more. It becomes a way of life for us.

#11

I found Christian Vlat Zot’s ketogenic research books Ketone Power: Superfuel for Optimal Mental Health and Ultimate Physical Performance and Periodic Fasting: Repair your DNA, Grow Younger, and Learn to Appreciate your Food to be info-packed and relevant in terms of a way of life that isn’t constant grazing/snacking and the powers of fat-adapted resting of the digestive tract.

Also this new documentary film talks to various researchers on the various kinds of metabolic changes that happen with shorter eating windows/IF - and keto-oriented Jason Fung MD is in it along with many other researchers and self-experimenters. Am looking forward to watching it myself.

http://fastingmovie.com/

#12

Yes, a satiated way of life and superfueling, not a DIET. :smiley:

(Gill Tritter) #13

Nullius in verba. I know people on 18/6 lose weight. Has anyone who changed from grazing to 15/9 lost weight?

(charlie3) #14

With my work schedual and commute time I end up at 15:9 more often than not. I don’t think it makes an important difference. There is more to restricting eating times than just the timing. In the bad old days I ate something 35 times a week, 21 meals plus 14 snacks. Today I eat 2 times a day 6 days and eat nothing on one day and no snacks ever unless you want to count zero carb flavoring in drinks. That works out to eating just 12 times a week. My hunch is that eating less often is health promoting regardless of calories.

(LeeAnn Brooks) #15

Thus the fasting part. Lol.

Even having breakfast is breaking a fast from sleeping, thus the term “breakfast.”

But there hardly a difference between 15:9 and 16:8. Though the more you push the fast number, the more benefits you will get if you are working towards EF.