Intermittent Fasting


Welcome to the third Primefit Nutrition Seminar.

This is a very popular nutrition topic and a big trend, but does it, in fact, deserve the hype? Intermittent fasting. I uncovered so much in my research, I've split it into two parts. Everyone else's loss for not coming, because it's really interesting what's coming out of that.

So These are some common questions I get as a dietician I want to answer today. What is intermittent fasting? Is it superior for weight loss compared to other diets? What are the actual health benefits of intermittent fasting? I often hear claims that there's so much science backing intermittent fasting. Should I try it to live longer? Should I skip breakfast? Basically, I want to answer - is it just a fad or does it deserve the hype.

 There are some other questions that I want to too, and this is: Why is calorie restriction and dieting so hard? We'll take a look at what happens to your body when you're fasting or dieting. What are the risks associated with intermittent fasting? How does it actually affect appetite, particularly on the fasting days? Can I follow it while I'm training and exercising? Can I do intermittent fasting and retain my muscle mass? A lot to get through just for part one. But if you don't understand something as were going on, just let me know. Heaps of time for questions at the end.

Do you mean you're doing it over two different days?

Today will be part one. There's so much on intermittent fasting now, it's a little bit confusing, as you can see there, illustrated by all the different things that come up when you think about intermittent fasting, or hear about it. It's actually been around since the '90s. If you google it, this is what comes up. It's pretty overwhelming. Love yourself and intermittent fasting. Interesting messages out there. What actually is it? It's significant energy intake restriction. Restricting about 75 to 90% of your daily energy needs, generally on one, up to three, days a week. These would be the fasting days. Generally, you knock down to about 500 to 600 calories a day, with ad libitum food consumption on non-restricted days, so your fed days.

Here are some of the different methods of intermittent fasting. The 5:2, alternate day fasting, the two-day fast, or the two-day diet, once a month fast, also known as the prolong diet, time-restricted feeding, and the 16:8 method. There are other ones which now exist but I probably don't have time to talk about today, and that includes eat, stop, eat, which is a 24-hour fast once or twice a week, your Warrior Fast, which is fasting in the day, eat a huge meal at night, or spontaneous fast, skip meals as and when convenient, if that's ever convenient, really.

Off in the corner there, there's now an app called Zero. Of course, there's an app for that. You can actually choose amongst these regimes which one suits you best and sync it up with your circadian rhythm and all those interesting features that come along with apps.

 Let's have a little look at traditional gold standard for weight loss. What this is is daily continual calories restriction. Most people have heard about this at some point. Basically, energy in equals energy out. So to see weight loss, we have to incur an energy deficit. Generally, what's recommended is to reduce energy intake by about 20 to 50% of your total energy needs. So what your total energy needs is what you would burn in a day, factoring in things like exercise, to see a reduction in body weight.

Speaker 1:            As an example, if you're burning that famous 2,000 calories a day, if you reduce to 1,500 calories a day, reduce the energy intake by 25% ... That's 500 calories. Hypothetically, that results in that famous one kilogram weight loss in a week. That's because one kilogram of fat equals about 3,500 calories. If you're causing a deficit of 500 over seven days, hey, presto, that's minus 3,500 calories and about one kilogram of weight loss.

This is the gold standard method. It's been around for a long time. Let's call this continuous calorie restriction, or just calorie restriction, CR; I'll refer to that that way throughout the rest of the presentation, or just conventional dieting.

The health benefits of calorie restriction in animals. We've known since about the '30s restricting our energy intake, or restricting animals' intakes, without inducing any kind of malnutrition or nutritional deficiencies, actually increases lifespan in these experimental animal models. It's been proven in quite a few now, like mice, flies, yeast, worms, and recently shown in monkeys.

 As a result of calorie restriction, animals are leaner, with less body fat and smaller, so more on the left-hand side in that there. Lifespan was actually extended beyond the average lifespan. Interestingly, as calorie intake reduced, lifespan increased. There was a bit of an inverse relationship, quite a strong one. But this is in animals. If we took a look at the animals' cellular health on a cell basis, the calorie-restricted animals were physiologically younger than ad libitum fed animals, when they had access to everything that they wanted. Calorie restriction actually prevented chronic disease development, particularly in mice, improved insulin sensitivity, a consideration for metabolic health ... Everyone know what insulin sensitivity and resistance is? Yep.

Also reduced inflammation and reduced oxidative stress markers. I spoke about that a fair bit in the last seminar about inflammation. It also enhanced immunity. About what percentage of energy reduction is this thought to happen at? As little as 25%, so in theory, that 500-calorie deficit in overall energy intake, up to about 60%. They cut it off at 60%. They didn't go any further than that.

Calorie restriction in humans is a little bit more difficult to study because we live a long time. The researchers probably wouldn't live that long.

Health benefits of calorie restriction and intermittent fasting have been investigated, but they're not as concrete. But what we have found, it's not just about weight loss. That's where the hype is with calorie restriction, but really, what we want to do is maximize our health and reduce our risk of developing chronic disease, like diabetes, cardiovascular disease. We want to know, how can we maximize our longevity, and this intermittent fasting, can that play a role?

The benefit of calorie restriction in general is that, yes, it improves our metabolic health-span. It reduces diabetes risk. It might work even better than some medications, like Metformin, to improve blood glucose tolerance and bring down blood glucose levels. It also reduces cardiovascular risk factors, like it improves blood lipids, so in particular reduces bad LDL cholesterol, reduces triglyceride levels. It also can reduce fatty liver. It's associated with a lower risk of developing several cancers and can help to reduce inflammation and improve biomarkers of longevity.

Similar to the animal studies, markers of oxidative stress and whole body inflammation reduced. What's really interesting, as well, like what they found in animal studies, is this enhanced immunity pattern. If your calorie restricted, you're actually more resistant to mild stresses. You can actually respond a bit better to that stressor than if you were eating to an ad libitum diet.

Intermittent fasting benefits are pretty much the same, it's come out. Improvements in cardiovascular and metabolic health, reducing blood pressure and heart rate, reduction in glucose and insulin, triglycerides. Also increases good cholesterol, HDL cholesterol, reduces markers of inflammation. Particularly in intermittent fasting, what we see is the body shifts in which kind of fuel it runs on. On the days when you're fasting, there's an increase in burning fat and reduction in burning carbohydrates.

Has anyone ever heard someone say this? I feel so much better after a day of fasting. I feel like it's

 Well, there might be something to it. Is calorie restriction a bit like exercise? Does fasting and energy restriction actually provide the stimulus to improve health? Some studies suggest that this fasting, this restriction of energy might be like exercise, in that it's a minor metabolic stressor, and it might activate pathways to rejuvenate cells and improve health and keep them physiologically young.

Why might this be? Why would there actually be benefits to calorie restriction? This is my take on it from the research. Is it perhaps that fasting is part of our genetic makeup, our genetic programing as humans? Maybe linked back to our hunter/gatherer days, when there were inevitable wars, famines that weren't predictable. It's interesting, in almost every religion, there's some kind of fasting or abstinence from sustenance component, like Lent, Orthodox Greek might fast once a week, one day a week, and then Ramadan.

My theory behind this is that our bodies are still stuck in the Stone Age. Our bodies have evolved to be very efficient at storing energy, and any excess energy, for later from the foods and drinks that we have. This would've provided us stores for that inevitable famine that might have come, or food scarcity during pretty harsh times, like harsh winters.

 In our evolution, it would've been very normal for us to have gone through these periods of fasting, depletion of stores and periods of feasting, repletion, depending on the availability of food. The problem is, it's only been less than 100 years in our physical environment where food has been in plentiful supply. World War II was only about 70 years ago. It hasn't been that long. Our thrifty genes and thrifty energy storage mechanisms which helped us survive in the past might actually be working against us a little.

There hasn't been enough time to develop any kind of opposite regulatory mechanisms in response to the far more common problem we see now than famine, which is over nourishment. Perhaps, that's why there's these benefits. Maybe we are programed to fast. It's in our genes. But let's not beat around the bush. The benefits of calorie restriction sound great in theory but, it's really hard to stick to. Calorie restriction, in general any kind of diet, any kind of fasting, but we'll talk a little bit more about why next time, it's not just you. Your brain and body and all your hormones work against you when you're in starvation mode.

Psychologically, adherence and motivation is generally pretty low in this continuous calorie restriction, if you're just reducing it a little bit daily. It can be really frustrating for those who are on a calorie-restricted approach for weight loss.

I know Michael Mosley promotes adding a bit of salad and a small can of tuna for lunch. It's a little bit like fasting. But what if intermittent fasting can offer an emerging alternative to that good old traditional approach?

Let's actually have a look at the evidence. As there are so many regimes that we've seen, it's actually quite difficult to compare studies. But let's take a look at the most famous, the most popular, the 5:2. This is Dr. Michael Mosley advocates for two fast days per week. That's 500 to 600 calories on those days, depending on whether you are female or male. Males get a little bit more. Doesn't generally advise when to eat during the fasting period. Although he does suggest some meal plans and certain foods to have a small breakfast, lunches and dinner.

This 5:2 has actually been the least well studied, which is interesting. Compared to continuous restriction, calorie restriction, there were the same improvements in insulin and glucose, which are these markers for longevity and living, living longer. Although the 5:2 appears to, on the days where you're fasting, be able to reduce triglycerides more effectively, a sign that you are burning your stores.

There was a recent study done last year. It examined overweight men and women over 50 weeks. In the intermittent fasting group, participants were told to eat for five days without energy restriction. Then on two nonconsecutive days, eat only 25% of their regular energy recovery amounts, about that 500-calorie mark. Then in the continuous calorie restriction group, participants were just told to cut down their calories by about 20% each day.

Interestingly, both the groups end up with 80% of their normal energy requirements overall. They cut down overall, over a week, 20%. In that case, with 25% of intake twice a week in the intermittent fasting group, where they're only having about 500 calories a day, that's causing an energy deficit of 1,500 calories twice a week. That's about 3,000 calories overall.

Say, in the continuous group, continuous restriction, if they're having 20% less daily, that's 1,600 calories a day, and they're restricting seven days a week, about 400 calories, that also equals about a 3,000 calorie deficit in one week. Does that make sense? But did the approaches result in distinct differences?

Actually, both groups gave similar results, which isn't really a surprise if it's the same energy deficit. But there was a slightly greater weight loss with the intermittent fasting, about 7.1% body weight change versus 5.2%. But beyond this small difference all the biomarkers of longevity over the 50 weeks were essentially the same. However, what's interesting is in the continuous calorie restriction group, they show no changes in how much energy they expended daily through exercise. They didn't stop going to the gym each day. Whereas in the intermittent fasting group, there was about a 13.4% drop off in how much energy was burned through exercise. This suggests that on some days, the intermittent fasting group just didn't have enough energy in the tank to go burn extra calories at the gym. That's an important consideration, as well. This is actually the most well-studied in the scientific literature. Alternative day fasting. Has anyone heard of this one?

Yeah. There is a little money in the weight loss industry so that is something to keep in mind with any of these regimes. What this alternate date fasting protocol calls for is fasting one day. So small caloric intake similar to the 5:2 in that its about 500 calories. It's advised to eat all daily calories at breakfast, or break the fast at lunchtime. So don't have it at dinner, have it earlier in the day.

 And then have as much as you want on the other day, and then repeat. So every other day.

Speaker 5:            Monday, Wednesday, Friday.

Speaker 1:            Yeah.

Speaker 5:            Sunday and then it'd...

Speaker 1:            And then Tuesday, Wednesday,

Speaker 5:            It's there that you don't have another life, that you're not likely to go out and have a lunch or get your dinner or something

Speaker 1:            Exactly, makes it pretty restrictive.

And then of course don't overeat on the other days if you want to lose weight. There is a lot more scientific evidence on this side, and particularly in mice what they've found even without weight loss it seemed to improve lifespan. So this study showed ... these studies have shown that it's linked with longevity.

 So it implies that there's some kind of independent benefit of fasting even in the absence of weight loss. There were improvements in insulin and blood glucose that they were the same as continuous calorie restriction. And both in continuous calorie constriction and alternative day fasting there was a reduced risk of diabetes independent of weight loss.

What about over two to three months and long-term? So over about two to three months they compared an alternative day fasting with continuous calorie restriction where they were reducing 25% a day. And overall there were reductions in body fat, about 4-8 kilograms in both groups. However, compared to the continuous calorie restriction there was a slightly greater weight loss in the alternate day fasting. However, looking at 12 months, there's no difference. No difference in the long term.

Speaker 5:            Certainly saves a lot of time only eating once a day.

Speaker 1:            And both approaches reduce glucose, insulin, cholesterol and other health markers. So both reduced diabetes risk and cardiovascular risk, and there were improvements in longevity markers, oxidated stress, anti-inflammatory markers. But is this maintained in the long-term? We're not quite sure.

Speaker 5:            If you then get to your goal, would you keep on doing it?

Speaker 1:            Hasn't been looked at.

Speaker 5:            Just keep getting skinnier and skinnier and then becoming anorexic.

Speaker 1:            Well that's what some of the animal studies have shown that as in keep reducing and keep losing weight, lifespan increases, but you have to think where is that cut-off point?

Speaker 5:            Yes. I still have visions, unfortunately, of people in the war where they were absolutely starved. You wouldn't want to get to that stage or become an absolute obsession and that's what happens with these girls that then become anorexic unfortunately. It's never enough.

Speaker 1:            You can become very preoccupied with food when you're fasting for months. So that's another thing to consider in choosing an approach.

Speaker 1:            So between these two there's no real difference between continuous calorie restriction and alternate day fasting in terms of weight or health markers when you're on. So they both improve your health.

Speaker 1:            Interestingly over twelve months, like we've been talking about, it seems that the alternate day fasting is just way too hard. Was this because it was just too much hunger to do it and this preoccupation with food, thinking about food all the time. And most people actually trended towards just bringing down what they were having each day by a little bit naturally.

Speaker 1:            But in the short term it seems there were lower dropout rates with the alternate day fasting, maybe people thought they could stick to it for two to three months. They were really compliant, really motivated, and stuck to it.

Speaker 1:            What about in the three weeks? Perhaps it is more superior in the short term? Because it seems people can't really eat on their non-fast days to compensate the eating so little on the day before, to maintain their body weight. We do see over three weeks about three to four percent reduction in body weight, about 2-3 kilograms. And we do know that fat was in fact being burnt, because triglycerides were dropped.

Speaker 5:            And suppose it'd be, stomach gets smaller when you're eating less. I get meals served to me sometimes and I say ... just even looking at it.

Speaker 1:            Yeah.

Speaker 5:            Can't eat that much.

Speaker 1:            There is something [crosstalk 00:24:15]. They haven't researched it enough but I think there is something to that and one of my recommendations is based on that as well.

Speaker 1:            So what appears to be happening here is in the short-term, maybe these intermittent kind of fasting approaches might yield a slightly better benefit for weight loss? Perhaps it's a good short-term strategy to shift a small amount of weight, so like, 2-3 kilograms over a few weeks. And then, as I mentioned, weight loss maintenance ... we're not sure. Because the studies haven't been done beyond 12 months.

Speaker 1:            So then there's something else called the two-day diet. It's similar to the 5:2, except the two fast days are together, so they're consecutive. Followed by five days of unrestricted food and drink. So there was no differences to continual calorie restriction, the gold standard, in terms of weight loss; both lost the same amount of weight. However, metabolically, this one did seem to have a significant impact. So really reduced fast in glucose, in insulin levels ... more then the gold standard. And improved insulin sensitivity.

Speaker 1:            Maybe this one might be a bit more beneficial for people who have pre-diabetes or really need to look at their metabolic health. However, in the long-term, we still don't know.

Speaker 1:            This is the latest one, in terms of imitating a fast. It's a once a month fast. And what it is, it's a low protein diet for five consecutive days, once a month, and calories are restricted to 800 calories a day. So what this guy's trying to do is mimic famine perhaps more similar to how we would've evolved so we might not have had much for almost a week. But then hunter gatherer's go out, get a big feast for the village, and then ... you know.

Speaker 1:            So it's not eating for the remainder of the month. And he advocates for products to have during that time.

Speaker 5:            Prepackaged.

Speaker 1:            Prepackaged. Very limited evidence in this one, there's been no human investigation yet.

Speaker 5:            Do we have that here in Australia though? Or is this somewhere else.

Speaker 1:            I've seen it.

Speaker 5:            Yeah.

Speaker 1:            But it's not easy to get your hands on it. I don't personally recommend this one because I don't think there's enough research around it yet. There are reduced risks of inflammatory diseases in yeast and mice, including cardiovascular disease, cancer, and diabetes compared to those who were fasting, they didn't look at weight. But it did increase lifespan and immunity so something's going on with fasting.

Speaker 1:            There's also the time-restricted feeding approach. So this advocates for eating normally everyday but with your biological clock times, you might have heard that kind of "don't eat after 8pm" ... has anyone heard of that before? To try and have an early dinner, don't eat after a certain time. Most people are eating anywhere from 6am to 11pm and onwards, so that's fifteen hours a day of eating, and maximum of burning 9 hours of fasting. So instead, maybe looking at a window of 10 hours of eating and fourteen hours of fasting is more ... mimics what our natural body clock would've been. And so what would that look like? Maybe waiting to eat until about 9am, and then not having anything beyond six or seven.

Speaker 1:            So studies have shown that a lot of people ingest a majority of their calories later in the day, and it's been well-known for about ten years that eating outside of our biological clock can actually alter it. We always knew it affected our brain, but it turns out it can actually affect our metabolism. So it can affect our liver, our muscle, our hormones and our body's fat clock.

Speaker 1:            Some justification for keeping within our natural biological body clock. A study was conducted in simulated ship workers in a lab and it was really interesting what they found. If they ate during the day and cut off by midnight, they had really good metabolic health, but those who ate after midnight almost gave themselves diabetes.

Speaker 5:            Very interesting.

Speaker 1:            I quite like this approach, it mimics more what our natural circadian rhythms would've been like. Particularly when we were evolving, we would have risen with the sun and gone to sleep when it got dark. And not having to fast for a long period of time makes it a much more viable alternative to this very strict fasting diet.

Speaker 1:            A couple of drawbacks of course, there are limited studies done, and weight loss occurs but it's really slow. So it's only like two to three kilograms over three to twelve months. But if it's going kind of unnoticed then that's a nice benefit. And usually intake is reduced, so it will have some metabolic health improvements but we're not sure about that in the long term. And it's probably not as effective as continuous, the gold standard continuous calorie restriction.

Speaker 1:            16:8. Have you guys heard of this one?

Speaker 5:            Yep.

Speaker 1:            Yeah. So it's kind of like the new 5:2 where you eat as much you want for eight hours, and fast for 16 hours. Similar to not eating after 4, or skipping breakfast. As we can see, it's also similar to time-restrictive feeding with different hours. However, it's not quite the same as the other intermittent fasting approaches, because there's no defined calorie deficit, you can eat as much as you want.

Speaker 1:            What we've seen in Ramadan studies which is the closest human model that we can emulate with 16:8 is that during Ramadan, Muslims will fast from food and drink from about sunrise until sunset and, depending on where they are in the world that could actually vary from about 10 hours to 16 hours of fasting.

Speaker 1:            But what's really interesting is daily energy intake is the same before, during, and after Ramadan. So it might drop off a little bit in the first week, but then they bring it back up again and no one loses any weight, which I think is quite interesting. And what tells us is adults are very capable of making compensatory changes in food take in response to a short-term fast to maintain their weight. So they can eat a lot in the evening and that's what we generally see is they eat a lot, and lots of energy dense foods in particular, like dates.

Speaker 5:            Do they only eat the one meal then?

Speaker 1:            No it's just they can...

Speaker 5:            So they start at sunset, and then sort of eat through until they go to bed which is also not a good thing. Actually, one of my granddaughters has a Muslim boyfriend and so I'll have a chat with him. Because he was at Ramadan and we were having ... and he just sat there which was, you know, really good, and he said "no I'll have this later".

Speaker 1:            Yeah, it's interesting how those religious components in fasting exist. I think what's encouraged is not to have too much, and the whole idea of Ramadan is to give to the poor. So what you're not having, to give it away. In terms of weight, and calorie ingestion.

Speaker 5:            It's advancing, yes.

Speaker 1:            So we able to compensate those clever regulatory mechanisms that we got to ... not let us lose weight, basically.

Speaker 1:            I don't approve of the 16:8 because of this effect, it's very likely that you can compensate for the calories later in the day, and as we've seen eating later in the day is not necessarily great for your health. May not be with healthy choices in the face of hunger.

Speaker 1:            It also doesn't really teach you to eat well or healthily. There's no defined calorie restrictions so you might miss out on the benefits associated with calorie restriction, not guaranteed to lose weight, could interrupt your body's natural cycle, and it's more restrictive then time-restricted feeding. I have noticed with a few people it sets them up for having a bit too much.

Speaker 1:            Should I skip breakfast? There's a really interesting study done with people with diabetes and intermittent fasting approach. They lost more weight and had better health profiles if they ate breakfast and lunch compared to if they had lunch and dinner. So out of that study ... that was quite a significant one ... it did seem like the breakfast meal was the important meal of the day.

Speaker 1:            And because breakfast could mean many things, it's quite difficult to answer that question and compare different scientific studies. What we do know is that particularly in Australia, Adults who eat breakfast are more likely to be a healthy weight, have a lower BMI and healthy waist circumference, compared to those who skip breakfast. There's also really great benefits for including breakfast. It positively affects the appetite regulation from satiety. Overall in the day you're more likely to have a lower intake of calories, and more likely to choose healthy foods. Particularly including protein, may not only help to manage hunger but minimize the loss of lean muscle mass while you're dieting.

Speaker 1:            It increases how much energy you actually burn throughout the day. This is the main point that I really drive home with people is that it sets your metabolism up to be optimal for the rest of the day, the body doesn't slip into any kind of starvation mode. And you're more likely to reach your daily fiber target if you're having that extra meal, less likely to raise and snack. So that contributes to better nutritional intake and overall diet quality.

Speaker 1:            So in summary, calorie restriction does work for weight loss and will have health benefits and there's definitely more then one way to go about it. In terms of intermittent fasting, these diets may lead to weight loss and are definitely a valid weight loss strategy. However, it's not superior to continuous calorie restriction, anywhere from 20 to 50%. That's probably related to the fact that the energy deficit created just becomes the same over a week. And the success of keeping it up in the long-term needs to be investigated.

Speaker 1:            So it's basically up to you! You can choose your approach and I can assist with making sure it's nutritionally adequate. Should I fast to live longer? As one of my favorite researchers puts it, well, yes, if you're a mouse. In humans it does appear to have some metabolic health benefits, quite a few, in the short-term, which are associated with longevity regardless of weight loss which I think's quite exciting. But in the long term, we don't know.

Speaker 1:            And from what we've seen in animal studies, weight loss is beneficial for increasing lifespan and it's very possible that if weight loss slows in the long term, we may not see these ongoing benefits of calorie restriction or intermittent fasting.

Speaker 1:            So I really do like the time-restrictive feeding approach, I think it's a lot more of a sustainable fasting approach, it means you can go out and socialize, it's not creating that kind of psychological barrier. It is a slower weight loss, of course, but I often recommend this, you can eat within your body clock hours during the week, it's a bit harder on the weekend. Think I do like a modified 5:2 in that way.

Speaker 1:            If you need some incentive for weight loss or you're really set on one of the intermittent fasting approaches, this is what I recommend. Making sure you actually get adequate nutrition. It's really hard, even for me as a dietician, to try and get everyone's nutrients in 500, 600 calories a day. And you don't really want to risk nutrient deficiencies with fasting as this can lead to detrimental effects to your health particularly with bone, muscle, and energy levels. Can really lead to fatigue.

Speaker 1:            I actually recommend formulated meal replacements if you wanted to go with this approach. They can help with adherence to intermittent fasting, and nutritional adequacy, notably approaching ... which can reduce lean muscle mass loss. And I'll talk more about that next time as well.

Speaker 1:            There are good benefits for quick weight loss supported by a lot of evidence, a big body of evidence, using specific perks. Particularly the liquid based ones, and not actually focusing on foods and ingesting proper solids, something about having a semi-solid food seems to have the benefit, is that maybe that we're not having to think about preparing foods, something to do with minimalizing intestinal distention and what that signals in the body, hormones, appetite hormones. And following intermittent fasting approach even just in the short term, 2-3 weeks, can actually be beneficial for incentivizing weight loss.

Speaker 1:            I think people like quick results, just in the short-term. I quite like opti-fasting, in particular this brand, because there's a lot of scientific evidence behind and it's not necessarily biased scientific evidence, it just doesn't ... been done by that company. Each of these products and there's a few different ones, there's shakes, there's soups, there's bars, and there's desserts. Each one of those products is nutritionally complete. What I mean by that, it's what you get from a proper meal. And it has adequate amounts of protein to stop your body stripping muscle if it's fasting.

Speaker 1:            Choosing two products a day, any of them, although the liquid ones seem to be a bit more beneficial and that will lead to about 500 calories a day and then I say throw in some extra vegetables, ones that aren't particularly starchy to make sure you get more fiber.

Speaker 1:            Really important that you eat balanced, healthy diet. I guess fasting day is not a reason to ... for not compensating for overdoing on the other days.

Speaker 5:            So are you suggesting the Opti-Fast on the 500 calorie days

Speaker 1:            Yeah. It's the best way to do it. The only drawback is that those products can be expensive but...

Speaker 5:            No, they don't work out that, no.

Speaker 1:            Just a little disclaimer. If you're someone who gets particularly hungry, or you're experiencing any mental health issues like anxiety or depression, or require high-level cognition and concentration at work, particularly for complex tasks I don't recommend trying this approach.

Speaker 1:            But in saying that, on fasting days, keep preoccupied with anything but food. And so these are the rest of the topics that I'd like to cover in part two. Any questions?

Speaker 5:            No that was interesting ... combination.

Speaker 1:            I'd like to see what evidence comes out about the 800 calories in a day, because I've noticed that seems to be a bit more sustainable for people then the 500 calories.