The FastDay Forum

Jennings - some words of caution about your chosen approach.

Frequent fasting results in high levels of triglycerides circulating in the blood and they can be taken up by the heart muscle which can become stiffened and its function is compromised. This has been shown in rats fasting every other day for a prolonged period. Back in the 1950s prolonged fasting was used as a cure for obesity but heart problems occurred in more patients than expected.

Please do not continue with this daily fasting lifestyle long term. I think that 2 days a week will prove fine as a long term weight control method but fasting daily may not be safe. Of course you will probably lose too much weight to be able to carry on indefinitely, but you should be aware that, like most things, too much may not be good for you. Two meals is likely to be fine but we don't know. Really I think the point is not to be in ketosis all/most of the time for many years. Also, IGF1 decreases with age and low levels can cause frailty (as seen in extreme age) so be sure not to cut your protein too much.

Sorry to have to dampen your enthusiasm...

Hi Carorees , I just read this and wondered if what I am doing is in this same bracket.
I am not eating until mid afternoon every day but then I either have the 500 cals or I eat what i want on non fast days. Is this the same thing and should I then eat earlier on non fast days ? Confused now.
Barbara

[carorees]

Barbara, it depends on how many calories you are eating on your feed days...do you think you are eating a normal amount? The method of IF where you have an "eating window" usually involves two large meals so that you get your required calorie intake but in a shorter timespan. People doing this don't also do 5:2 so we don't know what effects combining the two approaches would have. I assume that if you are eating up to TDEE on feed days that's fine.

My understanding of what Jennings was doing was to have quite a severe calorie restriction every day. In that situation there is a risk of inadequate nutrition as well as the high cholesterol levels you get with prolonged fasting. Also as he is older it is likely his IGF1 levels would be lower than in a younger person and as very low IGF1 is associated with frailty, all these things lead to my concern over his long term health.

Your situation could be different...if you are younger and eating more on feed days the same arguments do not apply.

I would be wary of applying two powerful interventions into your lifestyle in one go! So, I think that skipping breakfast every day is fine but would be cautious about skipping breakfast and lunch and doing two reduced calorie days!

It may be fine but we are all doing a bit of self experimentation here so it is prudent to be cautious.

I do care that no-one gets hurt from this you know!

Hi Caro and Jennings , I dont feel old but I am 60 so heading there I suppose.
caro, the reason I took to eating just later in the day was that from what I can see you need 18hrs ish from when you have digested your last meal to when you start to burn fat. if I eat a large meal at 6.30pm it will probably be around midnight before I have finished digesting it.Therefore from Midnight to 5pm is the fast window.I cannot do that long I'm afraid so have opted to have a small meal between 1&3 pm and then my main meal. I am eating a lot of fats on non fast days and feel quite stuffed so although I havnt tracked as such I think I am getting plenty of food and suddenly I seem to have broken through the plateau that I had been on for a few weeks.
Thanks for your concern and all comments welcome especially if I have misunderstood any of this.
Barbara

[carorees]

Surely its 18 hours since you last ate not digested? Need to check. The most common eating window form of IF uses an 8 hour eating window so that's 16 hours since the last meal.

Hi Caro, so ,if I finished eating around 7pm a 16hr fast would take me to 11am. Which was roughly what I was doing .I think the confusion is ,does the fast start when glycogen stores are depleted ,six to eight hours in this article below ,rather than when i finished my last meal of the day..
Barbara

http://fitness.mercola.com/sites/fitnes ... n=20130301

[carorees]

Hi Barbara

Yes, 11 am so you have a normal lunch and dinner and just skip breakfast. However the folks using the 8-hour eating window approach are not also doing a twice weekly reduced calorie (500 cal) day as well, hmm? As we have not much idea of how 5:2 works or the 8-hour window method, we have none at all on whether combining the two is a good idea or not!

The article you linked to suggests that the body starts to shift to fat burning after 4-5 hours not that glycogen is actually depleted (this takes up to 4 days for some people). The article suggests that you should aim to have 16 to 18 hours between dinner and breaking the fast the next day.

I get the impression that the 5:2 regimen works on the feast:famine idea so that feast days should involve eating around TDEE while famine days are the 500. The 8-hour eating window results in a daily calorie restriction unless you are careful to consume up to TDEE during the window. So I would guess that combining the two requires you to ensure you consume up to TDEE during the 8 hours if you are to benefit from the reduced calories on the fast days. If that works for you, great.

Jennings, however, is going for the daily reduced calorie approach by having a single meal daily. That is another way of doing IF.

In the end you have to see what works for you. For Jennings, feast:famine did not work and daily fasting did. Which do you prefer?

Mercola writes:

Just remember, it takes about six to eight hours for your body to metabolize your glycogen stores and only after that do you start to shift to burning fat, but only if you are already adapted to burning fat by having your fat burning enzymes upregulated by the strategy discussed above, which takes anywhere from a few weeks to a few months, depending on how healthy you are.

I'm not sure what he means by "metabolize your glycogen stores." If he means deplete your glycogen stores, then it certainly takes a lot longer than that. I believe it takes someone on a zero carb diet about 36 hours to deplete stored (hepatic) glycogen. So what does Mercola mean?

[carorees]

As we burn a mixture of glycogen and fat most of the time, I suspect he means start to increase the amount of fat burned. I saw it can be up to 4 days to reach a state of ketosis but of course not having ketones in your urine does not mean you are not burning fat! Perhaps he means it takes 6 to 8 hours for the raised postprandial insulin levels (which prevent lipolysis) to fall enough to allow some fat burning maybe?

As we burn a mixture of glycogen and fat most of the time, I suspect he means start to increase the amount of fat burned. I saw it can be up to 4 days to reach a state of ketosis but of course not having ketones in your urine does not mean you are not burning fat! Perhaps he means it takes 6 to 8 hours for the raised postprandial insulin levels (which prevent lipolysis) to fall enough to allow some fat burning maybe?

Hmmm...maybe. In a non-diebetic, BG should fall to baseline in 3 or 4 hours after a meal. I don't know why insulin would remain elevated. In an insulin-resistant person (like most of us here, no doubt) it takes BG longer to fall, and insulin may never get to baseline.

I recall reading that there's a baseline "pulse" level of insulin that goes up when BG goes above 84 mg/dl (not sure what that is in British measurements), so the pancreas "thinks" BG should be 84 or less. But we clearly don't have to have BG at 84 or less to burn stored fat, or some of us would never burn fat, on any diet, ever.

Anyway, if IF actually works as advertised and improves insulin sensitivity, it should shorten the amount of time it takes for BG and insulin to return to baseline after a meal. I just don't see where Mercola is getting those 6 to 8 hour numbers.

[carorees]

Have split the posts on glycogen and fast length into a new topic as they were OT re the OP on blood pressure.

[carorees]

I found this study which looks at pathways of glucose disposal after a meal. They followed subjects for 6 hours after ingestion of a meal that contained on average ∼78 g of glucose. http://ajpendo.physiology.org/content/284/4/E716.long

Some interesting graphs:

ADF results at baseline, day 21 and day 22 :-

Fat oxidation (g/24 h) 64 ± 8 54 ± 10 101 ± 92
Carbohydrate oxidation (g/24 h) 175 ± 17 184 ± 24 81 ± 162

perhaps "fat burning" needs to differentiate "stored fat" and "eaten fat" as we clearly burn fat and carbs normally.

perhaps "fat burning" needs to differentiate "stored fat" and "eaten fat" as we clearly burn fat and carbs normally.

This article by Lyle McDonald may shed some darkness on the matter:

http://www.bodyrecomposition.com/fat-loss/insulin-levels-and-fat-loss-qa.html

On a tangentially related note... Once I am settled into 5:2, I plan to try an experiment of getting most or all of my fast day calories from coconut oil. CO is high in MCTs, which are supposed to be an excellent energy source (http://jn.nutrition.org/content/132/3/329.full), with near-zero impact on insulin.

Sounds like the heart is always utilising FFA

http://www.ncbi.nlm.nih.gov/m/pubmed/17081788/

I echo Phil's last point

[carorees]

This article by Lyle McDonald may shed some darkness on the matter:

http://www.bodyrecomposition.com/fat-loss/insulin-levels-and-fat-loss-qa.html

This article highlighted some interesting research on different responses to diet according to insulin sensitivity and linked to another interesting article, which I think deserves a thread of its own, so I'll start the thread and look forward to new discussion!