The FastDay Forum

For the scientists and engineers in the house.

There are posts about the 2 day diet book by Dr Michelle Harvie and Prof Tony
eg
viewtopic.php?f=3&t=364

and

viewtopic.php?f=3&t=4268

I haven't got the book but whats the diff from a physiological point of view or dietary principles or how we would do it differently if we were to switch from 5:2 to 2 day diet. I think the 2 day diet book follows the 5:2 principles but its different from what i briefly read.

Reviews here seem to suggest its a useful book whatever the differences on the useful recipes alone.

2 Day is consecutive days - probably biggest difference.
2 Day restricts carbs to 40g on the 2 days.
Rest of week on 2 Day is the Fictitious Mediterranean Diet
2 Day book has loose target of under 1,000 cals on each of the two days.

5:2 at its simplest is any 2 days at either 500 (f) or 600 (m) calories with 5 days eating sensible amounts / normally.

One of the reasons the 5:2 seems to work for me is the separation of the 2 fast days. It helps to keep me from "going off the deep end" and overdoing. The discipline of coming back to that fast keeps me in check and, in a sense, retrains me again to sensible eating.

When we used to score essays on big tests according to a rubric, after a break we would always start by scoring a couple to make sure we were back on the same track. Separated fast days do the same thing for me. They put me back on the proper track.

That said, today is not a fast day.

I agree

Whats the theory behind the consecutive days on the "2 Day Diet"

I have 4 days between my Tuesday and Sunday when i do the restricted eating and I think its too long but Wednesdays just dont work for me.

Whats the theory behind the consecutive days on the "2 Day Diet"

from the horse's mouth :-

22. Why two days?
We wanted to make a departure from the grind of dieting every day. For most people, daily dieting does not work because it is difficult to maintain. The two days, however, are achievable, allow long enough to reduce your overall calorie intake, retrain your eating habits and they may have additional beneficial effects on metabolism and disease risk.

23. Do I have to diet for two consecutive days?
We recommend that the two days are done together because many dieters find the second day as easy, if not easier than the first, as they have got into the habit of eating less. Doing the two days together also helps to ensure that you actually get round to doing the second day and it may have additional health benefits because it provides a prolonged period when the body is in a healthier metabolic state.

I have heard her (Dr Harvie) say that there are benefits from reducing glycogen levels and keeping them down for longer rather than recharging the next day, but she hasn't explicitly tested consecutive vs separate days to demonstrate this.

Ill stick to non consecutive thanks. Seems easier and more logical to me.. ideally with 2 or 3 days in between though my days are Sunday and Tuesday which just works out better in my lifestyle

We tend to be a bit anti the The Two Day Diet here because it is not what most (or in fact any) of us are doing - maybe you noticed from the posts?

The Two Day Diet is quite complicated in practice and requires you to modify your way of eating not just for two days per week but on the other five as well. This is because it requires to you to switch to a 'Mediterranean diet' as Phil has said. Phil may be right to be agin the Mediterranean diet but the balance of dietary opinion is definitely the other way - at least for now. Our 5:2 doesn't have any specific dietary rules except for the calorie restriction on the 2 non-consecutive days.

Another significant difference between our 5:2 and the Two Day Diet is that the latter is based on a scientific trial (carried out in Manchester, England in 2011) so their results are 'proven':

In clinical trials, dieters were more likely to stick to The 2-Day Diet than to standard daily dieting. Followers of The 2-Day Diet lost twice as much fat as those on a daily calorie-controlled diet, and more centimetres around their waist.

On top of the weight you'll lose - and keep off - The 2-Day Diet also has numerous proven health benefits associated with it including...
Reducing insulin and levels of other hormones and inflammation in the body known to cause cancer, heart disease and diabetes
Lowering high blood pressure
Improving well-being, mood and energy

That these have been scientifically proven has been disputed by Zoe Harcombe but she's probably wrong IMO.

For our 5:2 we don't have this sort of proof but it seems plausible that many if not all the same benefits apply!

Personally I don't think the two consecutive day thing is important in the Two Day Diet (and I think it was a big mistake of theirs to specify it, I wonder if it had more to do with it being easier for the trial?) The overall diet change (2 days when you are limited to specific foods mainly to cut out carbs, and 5 days 'Mediterranean') is what it is about. The Med diet is surely better for us than a normal 'Western' diet of cr*p?

I think there is some logic to the two consecutive days - she's restricting carbohydrates so the liver glycogen reserves will be depleted in the first day. Continuing for a second day allows further depletion or a day with more ketones, lower insulin etc which could be more beneficial than reloading the liver and pushing blood glucose and insulin up by having the second day as a feed day.

The restricted 2-day dieters ended up consuming 31% of their calories as fat, of which 10.7% were saturated, a bit more was mono-unsaturated and about 5% polyunsaturated. Protein was 23%. Calories 1241 / day average over week.

A RCT with 2 consecutive days vs 2 separate days 3 days apart would be required to answer the "consecutive or not" question. The answer may be different for carb restricted or other macronutrient regimes.

I tried the 2 day diet but found it very difficult to keep going. And what the hell is a mediterranean diet anyway? I gave it up within a matter of a few weeks. It just wasnt for me. Was just sorry I wasted my money buying the book - should've stuck with the freebie plan from the Daily Mail.

Thanks for the info.I agree 5:2o is more sustainable and doable.If any temptations come along easy to pass that over with the thought tomorrow is feasting day.Not that one should go over the limit feasting.

5:2 diet for me every time, its easy, it works and it achieves results! what's to change

p.s. If I was living in the Med I would follow that way of eating but I'm not LOL

I think what bothers me most about the 2 Day Diet (I have the book), is that for the 5 days you AREN'T fasting, you are really still dieting. You follow a portion controlled food exchange plan similar to the Weight Watchers I remember from the 1970's/80's. Yet in the studies I read, the 5 day Mediteranean diet in the book is referred to as "ad libitum." This is just not true. My understanding of ad libitum eating is that you just eat whatever you want whenever you want. The 2 Day Diet is portion controlled, not ad libitum. I just don't understand how they can get away with this.

Right now I'm starting 4:3. I lost successfully with 5:2 last year, but I went off it and gained the weight back. I'm doing 4:3 in hopes of losing a bit faster/getting better control of my appetite. I really wasted my money on The 2 Day Diet book.

It takes more than 2 days to fully deplete your glycogen. For most people it takes close to a week eating a 20 g a day Atkins diet. There's some evidence that some people carry a lot more than the average amount of glycogen, too, so they can continue to dump glycogen for weeks. The differing amounts of glycogen people carry explains why some people lose a lot and others very little when they start ketogenic low carb diets.

But I have seen NO evidence that depleting glycogen enhances weight loss or, for that matter, fat burning. There are tons of people who stall out for long periods of time on ketogenic diets, and all the large, long diet comparison studies show that after the glycogen is accounted for, people lose at pretty much the same rate no matter what diet they use. The low carb diet produces more absoule weight loss, but that is because of that lost glycogen.

The real difference between all these diets is that a doctor can't get a huge advance for a diet book unless he comes up with some new and supposedly magic twist. So each doctor makes one up.

5:2 works as well as it does because it makes it possible to create decent calorie deficit. The rest of the pseudo-scientific claims are just that, and most of them are based on studies of people spending much longer periods doing complete fasts or, worse, on rodent studies--which have been shown time and time again to be irrelevant to human metabolic issues.

[carorees]

@peebles this is how I understand it:

The two day diet and 5:2 fasting don't work by depleting glycogen but by reducing carb intake such that insulin levels fall so that when combined with the reduction in calories the lowered insulin permits conversion from glucose to fat as the fuel. When insulin is high, lipolysis is low. People who are highly insulin resistant are usually metabolic inflexible and slow to convert to fat burning, these people will tend to use up more glycogen than those who are not insulin resistant before they switch to significant amounts of fat burning. It seems likely to me that people who are metabolically inflexible would have bigger glycogen stores as their bodies will have been relying on glycogen as the fuel source. I don't believe that glycogen needs to be completely depleted before ketogenesis starts. Once fat adapted, glycogen stores are held in reserve for use during high intensity exercise and the body uses fat at lower exercise intensity as can be seen by monitoring the respiratory quotient in fat adapted athletes.
The two day diet is essentially two days of low carb to lower insulin and spreads the calorie restriction out over the week to some extent. 5:2 and other IF methods rely on the fasting period (when you're not eating any carbs) to both lower insulin and create the calorie deficit.

Carorees,

The explanation you give is one found in quite a few of the low carb diet books, but Stephan Guyenet of the Whole Health Source blog, a Ph.D. in neuroscience who has a much better background in nutrition and physiology than any of the M.D.s writing diet books, has published some interesting posts supported by quite a few quality cites that call into question the link between insulin and fat gain. They are worth a look.

You can find them here:

http://wholehealthsource.blogspot.com/2 ... il-in.html

http://wholehealthsource.blogspot.com/2 ... y-and.html

http://wholehealthsource.blogspot.com/2 ... drive.html

There are a couple more on his site which you can find via Google if you are interested.

Stephan started out as an enthusiastic low carb dieter some years ago, but after he thoroughly researched the subject he seems to have come to the conclusion that the science is much more complex.

He also has some very interesting posts about Omega-6 oils and obesity, and discusses the utility of eating very boring food while you diet, which is something I'm doing on my fast days, to eliminate the brain-mediated hunger stimuluses.


What I'm finding interesting about this 5:2 diet as someone who has more than 15 years of experience with low carb eating is that the diet forces me to stop eating all the fat and protein I am used to dieting on, so in effect besides cutting calories I am also eating very low fat 2 days a week.