The FastDay Forum

[carorees]

The ability to achieve ketosis after fasting can give an indication as to how well the body can switch to fat burning.

I found this paper from last year which describes a study in which overweight people on a weightloss diet were categorized according to whether or not they achieved ketosis after fasting (the length of the test fast is unclear but it looks like it was 24-36 hours as the paper says the subjects fasted through three meals). Those who achieved ketosis lost more weight during their calorie restricted diet than those who did not.

A previous studyshowed that obese individuals tend not to achieve ketosis during fasting. In this study they used people who were fasting for Ramadan (so around 12 hours fasting) and found that normal weight individuals started to show ketones in the urine after around 3 to 6 days, whereas obese individuals still did not show ketones after 20 days.

When the body lacks carbohydrates or protein, energy comes from lipolysis. Ketones are formed during lipolysis, which can then appear in the urine. However, for the body to be able to use ketones for energy, insulin levels must be low. A very low-calorie diet or a low carbohydrate diet should lower insulin and raise ketone levels. A study of overweight adults showed that a ketogenic low-carbohydrate diet can produce greater weight loss than low-fat diet, and that a ketogenic low-carbohydrate diet promotes a greater degree of decreased triglyceride level, increased high-density lipoprotein (HDL) cholesterol level than a low-fat diet.

This research suggests that, for the fastest weightloss, we should concentrate on promoting the ability of our bodies to burn fat, by keeping insulin low (i.e. by low calorie/low carb/low protein intake).

I think that these studies may explain why our questionnaire results found that people who lost weight fastest on 5:2 had longer fasts (over 20 hours) on fast days and changed their feast day habits to have fewer snacks, less sugary food, less carbs and more vegetables.

I think this is true because when I fast 6p-6p and only have a minimal 175cal soup for dinner combined with feast day no sugar only fruit veg protein none of the breads pasta or rice I have a better weight loss. The summer has been tough as I have added the carbo trio back into my diet and have had very poor weight loss results. I do think though that some people can tolerate the carbs unfortunately I am not one of them.

[carieoates]

I think this is true because when I fast 6p-6p and only have a minimal 175cal soup for dinner combined with feast day no sugar only fruit veg protein none of the breads pasta or rice I have a better weight loss. The summer has been tough as I have added the carbo trio back into my diet and have had very poor weight loss results. I do think though that some people can tolerate the carbs unfortunately I am not one of them.

Same here. I've only achieved good weight loss with the removal of carbs.
Great info though thanks a million.

Hi Caroline, thanks for this and also thanks for pulling the results of the questionnaires together. I've only just managed to have a look at this today on my works laptop, since my rather outdated version of Windows on my home laptop could not open the file .

I agree with you that it is difficult to make any firm conclusions with the questionnaire data due to the variability of time on diet/ starting BMI, but these papers would seem to give more credibility to the results obtained related to duration of fast.

From the 13 people in the big losers quintile who did >20 hr fasts, I'd be interested to know whether they lost the absolute most (realise that sample size is getting a bit small to really be significant....)

Thanks again, Julie

I was on Atkins in 2003 and lost about 25 lb in 4 month. Never knew that fasting promotes ketosis also.
So, does this mean that not only lack of carbs but just reducing everything initiates it?
I remember that on Atkins I never was hungry but, in the same time, I could not eat carbs as I wanted for very long periods. You should enter ketosis zone and stay there on Atkins. Once you eat more than allowed quantity, you are out of it. And a lot of efforts to enter there again.
Here, on 5:2, seems that this ketosis process goes back and forth very fast, because on the next after the fast you can eat carbs ( and I happily do).
Is it that fasting somehow accelerates ketosis and Atkins do not?
Very interesting and thank you, Caroline, for articles! .

[carorees]

Lack of carbs and protein (protein can be converted to glucose) promotes it. By definition, if you're fasting you're not eating carbs or protein (or anything), so fasting will result in ketosis eventually, but how long it takes varies. If your body is used to switching into fat burning (because you often fast/low carb) it will happen quicker.

This set me thinking - if everyone varies, then people should look out for symptoms to know they are in ketosis. Then they could organise their fasts around how quickly or slowly they enter into ketosis. I found the following info:

Early stage symptoms include the following:

Tiredness or fatigue
Headache
Feeling thirsty all the time
Dry mouth
Ketosis breath, which smells vaguely fruity and not terribly pleasant
Metallic taste in the mouth, particularly on the back of the tongue near the molars
Weakness
Dizziness
Nausea or stomach ache
Sleep problems
Cold hands and feet
Frequent urination

Ongoing States
As your body adapts to ketones, your symptoms may change or abate altogether. If you are using ketosis strips, your urine may still show ketones present, although probably in far lower concentrations. This is nothing to worry about. The amount of ketones in your urine does not correlate to the rate of weight loss.

As your body adapts to ketones, you may notice the following:

A "buzzed" feeling
Increased energy
Normalized urination frequency
Better sleep
Euphoria
Clear thinking
Sometimes low-carb dieters never seem to reach ketosis, or at least never have the urine test strips indicate excess ketones. This could be because exercising has used up the excess ketones or the urine is diluted from drinking a lot of water. This doesn't mean these people aren't burning fat, just that they aren't registering as technically being in ketosis.


You can see from the "As your body adapts" part that many of us who find fasts easier after the first few probably always enter this stage. Now I'm open to correction on this

I don't know if this helps or not but you can get urine analysis sticks off amazon if you want to test your urine for ketosis. I had some strange results when I first started fasting so it's probably best if you do this that you don't get caught up in random one off abnormalities.

Oooh that explains a lot of how I feel on fast days. Many thanks for the details everyone :0)

Wee smells like new mown hay when in fat burning. Notice new lows on scales if I get that symptom, what about pains I seem to get random pains in back seems to correlate whenI know I have achieved a successful 5:2 with cals around 400 mark

Thanks for that Caroline. Guess I'm doing something right then!

Re. the symptoms of ketosis - according to the Phinney&Volek bible, a lot of those could be due to lack of salt: salt requirements are higher when you're fat burning.

Re. ketones in urine: it's been said before but is worth repeating - ketostix only measure one of the three different types of ketones that are produced (acetone); false negatives are frequent because, if your body is functioning optimally, you won't get ketones in your urine because you're body has balanced energy! The only reliable check for ketosis is blood ketones: sadly expensive (about £5.50 per strip).

The body usually switches to fat-burning during sleep (when you're effectively fasting).

Thanks for all the information, everyone. Sometimes I feel like the exception that proves the rule, in that I lost weight easily without prolonged total absence of food. For the 3months that I was doing 5:2 I never fasted for more than 16 hrs. straight, (dinner to breakfast), I usually cheated on the calories a bit (600 Cal or so/fast) and I spread the calories out in 3 small meals, generally 210 C for breakfast, 110 C protein bar for lunch; 250 Cal for dinner. I did cut out high glycemic carbs on most fast days, but I relied on beans and veges and high fiber cereal, so it was still mostly carbs. As a vegetarian, I didn't have the option to include meat. I'd read somewhere early on that the definition of being in a fasting state was to have an empty stomach and I figured the total time spent with an empty stomach would be the same, whether I ate 600 C at once or 600 C spread out over the day. I assume I achieved ketosis, almost from the first fast, since I had most of the symptoms described by jmousey and I lost weight at the rate of a pound/fast; 21 pounds total. I tried to maintain with 6:1, but kept losing weight. So, I haven't fasted at all since mid-July and I am maintaining at a remarkably steady 126-127 pounds (I weigh daily). I've stopped counting calories (I had kept a daily food log), but I think I am sticking pretty close to TDEE. I think 5:2 fasting for 3 months somehow worked magic on my metabolism. I'm not going to take it for granted that I won't re-gain weight, but so far, so good. I wish it could be as easy for everyone, especially those who need to lose weight the most.

[carorees]

Some people seem to be able to enter ketosis a lot more easily than others. It seems to depend on your level of insulin resistance, glycogen storage capacity, exercise level and just luck!

[carorees]

Hi Caroline, thanks for this and also thanks for pulling the results of the questionnaires together. I've only just managed to have a look at this today on my works laptop, since my rather outdated version of Windows on my home laptop could not open the file .

I agree with you that it is difficult to make any firm conclusions with the questionnaire data due to the variability of time on diet/ starting BMI, but these papers would seem to give more credibility to the results obtained related to duration of fast.

From the 13 people in the big losers quintile who did >20 hr fasts, I'd be interested to know whether they lost the absolute most (realise that sample size is getting a bit small to really be significant....)

Thanks again, Julie

They were not all grouped at the top of the top quintile if that's what you mean? Their ranking in the top quintile was 2,5,10,12,14,16,17,18,19,21,23,25,26,27. So quite spread out.

The total weight loss ranged from 2.73 kg in 3 weeks to 12.2 kg in 15.5 weeks and the rate of loss per week ranged from 0.79 kg/week to 1.18 kg/week among those who fasted for over 20 hours.

They were not all grouped at the top of the top quintile if that's what you mean? Their ranking in the top quintile was 2,5,10,12,14,16,17,18,19,21,23,25,26,27. So quite spread out.

Hi, yes that was what I meant.

For me, the questionnaire results basically just show what we could have predicted anyway with any diet ie. those that lost the most, 1) had more to lose in the first place and 2) made more positive changes to their diet.

I don't mean this to sound negative though, because I really believe that 5:2's main advantage versus other diets is its sustainability over the long term. Maybe in 5 years time, someone will do such a study and prove this correct!