Welcome to The Fast Diet › The official Fast forums › Body › Science of intermittent fasting › Ketosis (Teaching the body to burn fat)
This topic contains 30 replies, has 18 voices, and was last updated by bigbooty 3 weeks ago.
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20 Nov 13
I have been on the 2:5 for about 6 months and lost about 10kg (over 20lbs) So thank you Dr Mosley!
A lot of the reviews of the fasting lifesyle seem to suggest that it is just a way to reduce average weekly calories, but I’m sure most of you think there is more going on than simple calorie reduction.
During the last 10 days I didn’t fast as I was on holiday traveling and found it difficult. Amazingly I did not gain any weight. This has happend on two occasions during the last 6 months.
I think the fasting days are forcing the body to relearn how to burn fat. I’m a bit confused about the correct scientific terms for this ‘lypolysis’ is I believe the breackdown of fats (into amino acids) and ketosis the burning of
fat as fuel.
What ever the terminology it seems like the fasting days teach the body a long forgotten trick of switching from available glucose derived from what we just ate, to reserves stored as fat.
I suggest that this trait applies to non fast days too, hence the lack of weigh gain during holidays.
I used to do a bit of distance running and am quite familiar with the concept of ‘hitting the wall’. This is when a runner runs out of glucose and has to switch to fat burning (around the 18mile mark). Often that process is difficult, I have had to sit on the ground for about 3 minutes until my legs felt like they would work again.
I’m not running now so I can’t try a quick marathon to see if the diet has helped with the switch.
I welcome your thoughts.
Perhaps Dr Mosely could weigh in on this with some scientific evidence.
I love science and this is why I love the 5.2 as it makes so much sense.
Your body will go into ketosis when fasting for a short time, this is probably why some people get headaches. It will also make you very thirsty and wee a lot as your body tries to flush out the by products from fat metabolism. This is a common symptom of type 1 diabetes but obviously they go into a severe more ketoacidosis due to prolonged lack of insulin and metabolism of glucose and start burning muscle for fuel.
It’s quite complicated stuff but if you google fasting ketosis there’s loads of interesting info online. Michaels book was lacking in any science stuff which is a shame as I think people are interested.
I know that athletes or very fit people are more efficient at burning fat as they are used to it so yes I think the 5.2 does reset the metabolism in a similar way.
I have managed to this this after years of cycling and find I can ride for a few hours on an empty stomach. Always need coffee though !!!
21 Nov 13
I’m also very interested in ketosis. I tried it out a few weeks ago and didn’t eat any carbs for 1,5 week. I lost quite some weight, but felt like I couldn’t sustain it – I started feeling really weak, dizzy, couldn’t walk straight some days and all in all didn’t get the energy boosts some people boast about.
So now I just cut carbs on my fast days and allow myself fruit and yoghurt on normal days – still prefer not to eat rice, noodles, bread and potatoes though. Sometimes a baked good or chocolate pudding as a treat, but not regularly. I do think this really contributes to my quicker than average weightloss (7kg in 3 weeks, of which most during that first 1,5 week).
I’ve also started working out fasted. I do this after work before my only meal of the day, so after fasting for over 20 hours. I do HIIT (Insanity), which combines cardio and strength through bodyweight exercises. So far my results have been worse than when I did the program before when eating regularly, but I’m waiting to see how it goes in two weeks when I do my second fit test. My body is most likely also learning how to switch to burning fat efficiently.
What you said about going on a holiday, this reminded me of the “carb loaders” I know. They basically cut carbs during the week, then they “carbload” on Saturday – eating everything from pizza to ribs to whatever they want. They say that it doesn’t cause them to gain weight, because the body is still in fat burning mode and the glucose from the carbs goes straight to the muscles, giving the muscles the strength to keep working out through the next week. Hence carb ‘loading’. These people are basically in ketosis 3 days a week (it usually takes the body about 3 days to go into full ketosis).
These are all bodybuilder types though, who do mostly strength training so it doesn’t really sound like a great idea for me. I wanna be lean, not buff.
Anyway, long post – gonna head over to the next one 😉
25 Nov 13
Hi Nika and Z
Thanks for your input, we don’t seem to have many other followers, perhaps this stuff is a bit too deep!
I’ll do some more digging and see what I can find on the metabolic demands switching from glucose to fat burn.
I wonder if any in depth study has been done concering what realy happens in the body when we switch fuels?
I’ll post any results I find.
All the best
I found this topic really interesting Rcroix so keep the info coming. When I did the marathon I didn’t hit the wall I think because I’d done my long runs to educate the body in fat burning but that was a while ago!
Nika-I used to work out in the fasted state but don’t now,nothing worse than running out of steam in the middle of a power press!
congrats on ur 20lbs loss!!
we have supermany followers of ketosis on nonfastdays
deep stuff as u say we like deep thinking 😀
look @ the reverse site
or the vids & lectures & tools on this site
everything a newbie/poster might want 2 c, use & read
hope this helps ur journey in this the fdl (fastday lifestyle) w/ ketosis wish u continued success
when u watch the vids of these dr’s & researchers
they point that the reason a mediterranean diet the lowcarb 1 has been applauded is because they fast
happy & nonfastdays & fastdays & 5/2 & 4/3 & 6/1 & adf or 4/2/1 or 3/3/1 or 5/1/1 or adf w/1 & the fdl (fastday lifestyle) & lchf (lowcarbhighfat) 😀
26 Nov 13
Hey Sonunda, I do HIIT with just bodyweight exercises so luckily I don’t have the risk of being crushed by weights should I suddenly slam into that energy wall 😉 Yesterday I found that it’s not really my breathing that’s forcing me to stop, but rather my muscles turning into porridge… From what I’ve read about working out fasted, that’s just the opposite of what other people tend to experience.
It’s a bit frustrating but I guess interesting as well… I’m planning on cutting carbs this week again, totally, and keeping up with the workouts. I really want to give it at least a week because I understand it takes your body about 3 days to go into full ketosis and I’ll just have to push through those days… Not really looking forward to that, but my biggest weightloss so far has been without carbs so I’ll just focus on that!
I read the book “The Paleo Solution” and I liked the ideas, however I did feel like he was doing some major propaganda for his own method rather than having a scientific approach to it. It does explain a lot more about the biological aspects of eating low carb and it basically follows a meal through the digestive track and the rest of the body step by step. Maybe it’s an interesting read for you?
Hi Everyone Martin again.
I have been doing a bit more digging on the fat burn subject. I am getting conflicting information about ‘Leptin’ the enzyme that is influenced by fat levels. One site says that increases in leptin cause the switch from glucose to fat burn but another says that calorie restriction causes leptin levels to decrease, which would contradict our thoughts that the fast days force fat burning.
Whatever the reality it seems like leptin is a key player. Perhaps Michael could chip in with some ideas?
All the best
Hi again. I don’t believe in cutting things out-I don’t especially want my body to go into ketosis. I’ve been following the 5-2 since July,have now lost 10.5Kgs dipping below 70 for the first time for ages. I’ve had no trouble fasting,no trouble eating sensibly on the no fast days and no trouble keeping up my schedule of 9 fitness classes a week. The good thing about this diet is that you don’t have to cut out major food groups like carbs,that would be the Atkins or the dukan diets,neither of which worked for me.This works,so if it ain’t broke don’t fix it.
27 Nov 13
I’ve consistently kept fat intake down on all days. I was talking to a couple of scientist on the weekend and they were skeptical about the fasting days. They had a rethink when I said these days were not consecutive.
This is my 4th week on 5:2 and my clothes are loose fitting.
I will refrain from saying anything to others until I’ve gotten past Christmas.
29 Nov 13
different people try different things. And yeah, you don’t HAVE to cut carbs, but some people just prefer it and are interested in it. You say the good thing about this diet is that you don’t have to cut out major food groups? I think the good thing about this diet is that it’s all up to you how you follow it / plan it. So if you don’t believe in cutting carbs fine, and I won’t lecture you on how bad some carbs are for the human body – just let us discuss our theories here 😉
Martin, I’ve looked up what the Paleo Solution book says about Leptin:
“Leptin regulates both appetite and metabolism. Leptin enters the central nervous system where it acts on receptors in the brain that control energy intake and expenditure. Leptin is produced by white adipose tissue (fat cells), as well as the cells lining the wall of the stomach. The leptin produced by the cells in the stomach is responsible for controlling appetite. When Leptin is working correctly, it’s very effective at telling us we are “full” after eating a meal. As we will see, when leptin signaling (how a hormone “talks to a receptor”) breaks, it is the beginning of problems ranging from cancer to accelerated aging to neurological degeneration.”
“The stomach is an acid environment that plays host to a small amount of protein digestion by the action of acid and the enzyme pepsin. The stomach is really just staging the food for the serious digestion a few stops down the line. Cells that line the stomach sense food and release leptin into the circulation. Leptin passes into the brain, signaling the appetite centers that we are “fed,” thus decreasing appetite, while increasing our metabolic rate in response to food.”
“It should not come as a surprise that our bodies have complex sensors that tell us not only if our blood glucose is high or low, but also how much total energy we have in storage. Leptin, which tells the brain we are “full,” is not only released in response to food, but it is also released from our body fat. This should make sense on a mechanistic level: A relatively large amount of fat will release a relatively large amount of leptin, which sends the signal “I’m full, no need for more food.” Conversely, if we are getting very lean and our energy reserves become low, our leptin signal will be low and we experience hunger.”
“It is also important to note that excessive carbohydrate intake leads to palmitic acid production. If you recall from the insulin chapter, when liver glycogen is full, additional carbohydrate is converted to palmitic acid. This process appears to blunt our sensitivity to leptin, which then inhibits our satiety to a normal meal. This is the beginning of insulin resistance and is at the heart of the mechanism of how we cease to respond to food by feeling “full.””
Okay, that’s all the book said about Leptin. Basically Leptin does not increase fat burning, it’s just something that tells us we are full. It is released by fat stores in our body, as well by our stomach lining when we eat. Anyway, I won’t repeat what has been said above, you’ve read it so I guess it’s clear what the book thinks 😉
14 Jan 14
I applaud everyone here. You are really dedicated and the pounds seems to be coming off in large numbers, too. I’ve lost 14 lbs., but haven’t stepped on the scaled for 2 weeks. I’m scared that I’ve gained since I’m not very consistent right now with my workouts, but then again, I always go through that inconsistency when I either get sick and need to convalesce. It’s a little hard getting back into my routine, but eventually, I get there.
I’m curious about your large weight loss by cutting out carbs on fast days. I’ve also noticed that Dr. Moseley did not have carbs for breakfast in his film. He only had ham & eggs. Hummmm…
I forgot, but in the film, was that his only meal of the day or did he have dinner that evening? I’ve changed my fasting routine a little to just having the one meal in the evening and staying busy during the day and drinking water and black coffee. Mimi (the co-author) ate 6 small meals during the day and you can see how slim she is.
I’ve been on the plan since March 2013, and was hoping to see more weight loss by March 2014. I’m not sure what to do. Any suggestions?
@ethereal, when you cut out bread, pasta, rice etc you haven’t cut out all carbs from your diet, you have just cut out the processed crap. As Nika points out in Paleo/primal eating you are still encouraged to eat plenty of fresh seasonal fruit and veg. These are carbs!
You may have to play around with your diet and see what works for you. When you do cut the processed foods from your diet you will notice some withdrawal symptoms because of their high sugar content. Stick with it, your body is so much better off without that crap.
For what is worth, my recent reading seems to state that the body doesn’t burn stored fat when there is insulin in the blood stream, so on the fasting days, having fewer of those spikes, gives the body a chance to burn fat – weight. With that and the reduced calorie intake over each 7 day week it explains the weight loss. And it sounds good for the body.
15 Jan 14
Thanks. I needed that!
8 Dec 15
This is a great thread. I’ve been reading up a lot about ketosis and how the ketogenic diet has been instrumental in the care and prevention of epilepsy and metabolic diseases such as Type 2 diabetes and cancer. After reading Gary Taube’s ‘Why we get fat’, and coming across Dr. Peter Attia’s site ‘eating academy’, I had to give this a go. I hope you don’t mind, I would like to share an anecdote of my personal experience with keto.
I’ve been experimenting with ketosis for a couple of months now. At first, I induced ketosis by eating a high fat and low carb diet rather than fasting. Although I have tried the 5:2 diet in the past, I found it was effective but extremely difficult to stick to as I would feel like death on fast days, so I thought maybe I should do keto and see how I feel.
I have been losing fat on the ketogenic diet despite being already quite slim. Last week I measured my waist to be 66 cm. Down from 72 cm a couple of months ago. However, weight loss is far from my mind. The reason 5:2 and the ketogenic diet appealed to me was that I have a scary family history of cancer, mental illness and, that’s right, Type 2 diabetes, suggesting that my genetics predispose me to a range of metabolic diseases. Anyway, if this intrigues you please read on.
For those who want to know a bit more about the ketogenic diet, the basis is this: you reduce your carbohydrate intake to 20g a day (not including dietary fibre) and you try to get the majority of your calories from good fats.This has the effect of not inducing an insulin response because you have little to no glucose which causes your body to switch over into ketosis. This differs from paleo or atkins in that both paleo and Atkins advocates high protein intake over high fat. Some amino acids can induce insulin production, which is a no no if you are aiming for ketosis. As such your protein intake should be moderate, not high.
As a vegetarian, this was a major struggle as the majority of my calories came from grains, bread and starchy vegetables. Bread and grains were the first thing I gave up, and for three weeks I did extraordinarily well. I ate a lot of avocados, nuts, and cheese and surprisingly, despite eating over 2000 calories a day, the weight dropped off.
Unfortunately I did experience the keto-flu for the first week. I was dizzy, light headed and I couldn’t do cardio exercises. I panicked and thought that I may be giving myself heart disease but upon further research, I decided to stick with it. I tried to remedy the dizziness with a lot more water, a greater in take of spinach and salt and that seemed to have helped. After the second week, I felt my fitness returning. I started doing HIIT for 7 minutes a day. I felt strong. The third week was amazing. My cravings were gone and I was functioning above optimal in terms of personal fitness, health, and suprisingly, mental health. This was without fasting, or counting calories. I ate as much fats as I wanted and as often as I wanted. I lost 2 kg of body fat and no muscle. and that was without cutting out my favourite starchy food, sweet potatoes. I must also stress that I was only working out 7 minutes a day. So the weight loss could not have come from exercise.
Another amazing side effect, I was able to go for longer periods of time without being hungry. I began just skipping breakfast and not eating for 16 hours just because I didn’t feel like eating. I was happier, more energetic and I could look at a carb without longing. Which was uncharacteristic for me because my nickname was Bread Monster and I use to lust over wholemeal sourdough.
Intrigued by the effects this diet had on my appetite and my mood, I decided to try 24+ hours fasts with only black coffee and water. For three weeks straight, I tried to extend my fast every time. I started at 32 hours, where I started hallucinating before the 30 hour mark. This was fun at first because the number 3 tasted like strawberries and the letter E tasted like ‘grey’. That’s right. I was tripping. That high quickly faded and I started feeling a sense of dread and despair. I knew I was imagining it but the feeling that I was going to die from hunger became real and had to woof down a cup of milo at 32 hours. That was not fun. I tried it again the following week and extended it out to 42 hours without any issues. Last week, I broke my fast at 47.5 hours without even the slightest bit of hunger, though I did feel slightly dizzy or weak, but that wasn’t the reason I broke it. I broke it because it was artisanal pizza night at my local microbrewery.
So from my own experiences I can only theorise that I’m training my body to switch into ketosis much more readily, which meant my brain wasn’t being starved of glucose. Every time I fast, my body gets better at producing and using ketone bodies. Which is why it gets easier and easier. I feel sharper, and more resilient after fast days, and I also never feel hungry anymore.
So some people may want to try keto for themselves, and one of the first things they’ll ask is how hard is it to keep carb intake to 20 g or less? Honestly, It’s completely doable, unless you are vegetarian. I think my carbohydrate intake is still high, at around 50-100 g a day. That can’t be helped. I don’t eat sugar anymore, none. Yet I can’t get my carb intake below 50 g a day because every vegetable and nut is a carb! As a result, I needed to keep my body in a state of ketosis via other means such as fasting. I also have a social life, which often revolves around food. Though I may avoid sugar like the plague, fruits, paleo desserts and the odd pasta dish and pizza do end up on the menu. This is another reason why I found that combining keto and 5:2 helped because it allows flexibility. Not to mention you save a lot of money by not eating 2 days of the week (more money for beer! Yay!)
I think for people who have an interest in the role of ketosis in mitigating metabolic diseases, definitely read Dr. Peter Attia’s blog. He uses a lot of science, but it’s understandable and accessible: http://eatingacademy.com/
If you want to know more about my experiences PM me. I will be fasting today and tomorrow. Will break it Thursday morning. Im working my way slowly to a 10 day fast, so if you want to join me, message me. I’m happy to have a buddy.
Hi lydiac and welcome:
I’m just finishing up a 10 day water fast. If you are interested in going longer than 40 hours, I suggest you watch this video – a couple of times: https://www.youtube.com/watch?v=6FOBa_hfbRE
Also, the Wikipedia outline of the ketogenic diet contains some interesting information: https://en.wikipedia.org/wiki/Ketogenic_diet
21 Jun 16
Recently became more interested in combining fasting and keto diet. Can anyone recommend a reasonably price blood ketone meter?
22 Jun 16
I use a Freestyle Optium Neo, they are pretty cheap. About $30-40 dollars. Look on ebay. Shop around for the glucose and keto sticks that the machine uses. If you shop around you can get them for 30 cents each for the glucose stick and about 70 cents each for the keto stick.
23 Jun 16
Thanks bigbooty…I’ll look for what version would be available in UK.
First time poster, long time lurker. I’ve only been doing 5/2 for 3 weeks without a great deal of weight gone but that’s ok, I’m here for the long term. With regard to training your body for ketosis,, you might be interested to read about the Maffetone method paraphrased as slow down to get faster. He helped Mark Allen become one of the greatest ultra distance athletes so he has cred. His point is that training a ketosis switch is related to heart rate. His general rule is 180- your age (- more if you are injured or unfit) in this rang you burn fat. The more you train in this range the more efficient you are at burning fat and therefore you can perform better in an aerobic state. Mark Allen wrote a great article about his experiences and I think it was called ho slower to go faster
I love this topic👍
24 Jun 16
Everyone burns a combination of glucose, glycogen and fat ALL the time, its the relative percentages that change depending on your energy state and what activity you are doing. I think from memory working at about 60% of your functional threshold performance tends to burn the most fat. FPT is an exercise effort that you can sustain for about 40-60 minutes before caving in.
There really isn’t any easy gimmick to operating in a ketotic state, you have to put in the hard yards. The liver is a two way street. It stores energy as fat and it retrieves energy from stored fats. Trouble is our modern eating habits means we rarely use the liver to access lots of stored fats as energy. Don’t use that part of the liver’s function and its unlikely that it will be working very efficiently. Just like training any muscle, if you don’t use it, its unlikely it will be operating at its peak. Its taken 9 months of water fasting two days a week (currently only doing one day per week) to train my liver to really crank out the glucose and ketones when fasting. Of late Ive had to consciously eat more than Ive wanted to as Im still slowly losing weight and I don’t really want to lose any more. Crazy to be posting that on this forum but that’s my situation at the moment. We eat so much sugar and processed crap. Im not a vego/vegan but I don’t eat a lot of meat. Personally I think grains and sugary anything and alcohol are the main culprits to today’s obesity epidemic.
15 Aug 16
From what I’ve read online it takes around 72 hours for the average male to go into a state of Ketosis (little less for a woman). So this leads me to two questions:
1. How do you start burning fat on an intermittent fast when at the most on a 5:2 diet with two consecutive days you will only fast for 48 hours?
2. At what time does the average body switch into cell repair mode from the normal ‘go,go’ mode suggested by Michael?
See my post above. You burn fat all the time. Just the ratios change depending on your fuel reserves and activity/intensity.
When I first started fasting it was two consecutive days Mon/Tues (so 60 hours). At the end of 60 hours I was just entering ketosis. This is not guess work on my part. I measure this with a blood glucose and ketone meter. They are cheap to buy. Ive been water fasting for 10 months now. I now enter ketosis after 24 hours and only fast for one day (36 hours) now. My definition of entering ketosis is a ketone level of 0.5 mmol/L or more. The longer you practice fasting the easier and faster you will flip over into a ketotic state. I do not eat a keto diet as such. I do however eat very minimal grain based foods and no added sugar.
16 Aug 16
bigbooty, I’ve got a blood glucose meter which I use and find very helpful. After reading your post I now realize there is such a thing as a keto meter! All I’d ever known were urine keto sticks, so I gather you’ve got the keto blood meter? If so, is there a brand or type you prefer? I like gadgets since I feel they help point me in the right direction. I see Amcal sells a ketone monitor for under $10, the Freestyle Optimum, though often the ones that are cheapest to buy can only be used with the most expensive disposables!
Thanks bigbooty. I forget that we do not class a day as 24hrs and therefore include sleep on both nights. I’m new to all this (within the past month) and reading up emphatically. Last week I managed 70 hours of water only fast and I probably could have gone longer but didn’t want to push it. In my head now it has given me a bit of a physiological boost. This started out being a diet based exercise but has actually turned into something far far greater than that for me. Watching Dr Mosley on the BBC Horizon programme (UK) has revealed aspects I would never have dreamed of.
I use the Freestyle Optium Neo. Its what they had at the local diabetic society shop I went to so that’s what I bought. You are correct the keto disposable sticks can be expensive. I usually try and buy them on ebay and wait for someone to have them on sale cheap. I then buy a large batch of them to save money.
I’ll usually only use one or two keto sticks per week after my fast so I don’t use that many per week. The glucose sticks are a lot cheaper and those I use on a daily basis or to monitor my response to different foods. That in itself is really interesting.
No probs. Happy to help.
1 Oct 16
Contrary to some earlier comments, you don’t burn fat unless your insulin level drops. You will always burn your carb reserves first. Carbs are glucose, raise blood sugar and insulin comes to remove this danger from the blood stream.
A low carb, high natural fat diet is the best way to lower insulin and fasting reduces it further. If your insulin drops you’ll lose water and salt with it, and probably magnesium, so add some to your diet. I also drink coconut oil and salt twice a day. Heresy to the NHS low-fat nonsense, but I’m the same weight as when I was in my twenties. Natural fat surpresses your appetite; carbs fuel it.
2 Oct 16
Hi. I’m also interested in this topic. I haven’t read all the posts but has anyone tried the Atkins Diet? This is a low carb, high protein diet and it’s aim is to go into ketosis, thus using our stored fat supply’s for energy. I lost quite a lot of weight on it but found it difficult to stay on long term. I like the idea of eating a minimum amount of carbs on fast days. Atkins reccomendation was to limit it to 20 gms. He also recommended taking extra salt plus multivitamins. He was not a fan of low fat either.
Just another thought. I don’t think it’s necessary to buy anything to measure ketosis. If you are going to the loo more often, ie passing more urine and are more thirsty than usual, you are probably in ketosis. The urine also has a definite odour. Ask any nurse who has worked with diabetics.
You are correct about the urination smell and frequency. Still probably worth investing in a meter if you are unsure of what to look for. Ketones will have a “sweet” smell a little like nail polish.
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