5.    Blood sugar and pre-diabetes

The food we eat is metabolized in our small intestine to extract its energy which is made available to the cells in our body through blood glucose.  The level of blood glucose is regulated by insulin produced in the pancreas but if this control mechanism starts to fail, and our cells no longer fully respond to the insulin, then we become “insulin resistant” and our blood glucose levels start to rise.  If this change occurs due to diet and lifestyle rather than illness, then the transition is likely to be quite slow with lots of advance warning if you have occasional blood glucose tests.   The Diabetes UK site provides loads of background material on blood sugar, pre-diabetes and diabetes :  https://www.diabetes.co.uk/index.html


Blood sugar can be measured by a blood test after fasting overnight and this will provide a snapshot of your blood glucose at that time.  Alternatively the HbA1c blood test measures changes in haemoglobin that relate to your average blood glucose  levels over the previous eight to twelve weeks so provides a much better view of your average blood glucose.  This is the test I had and my initial reading was 42mmol/mol which placed me right on the threshold of pre diabetes :


Normal :         less than 42mmol/mol

Pre-diabetes : 32 to 47mmol/mol

Diabetes :       48mmol/mol or over


After six months of 5:2 Fasting + Mediterranean Diet my HbA1C reading had fallen impressively to 36mmol/mol and was firmly into the normal range.  While I did not have a particularly sweet tooth to start with I removed all free sugar from my diet and the occasional chocolate biscuit became a very irregular treat.  However the biggest change was probably the elimination of refined carbohydrates like potatoes, rice, white flour, and pasta which are all just other versions of sugar.   Removing these had a huge effect on my levels of energy and tiredness so I guess they must have been adversely affecting my blood sugar in some way to cause such an effect.    They no longer form part of my diet (just maybe the occasional roast potato at Christmas!).


5.1  Carbohydrate tolerance and the amylase cracker test

Long after I had determined from the experience on the diet that I did not respond well to simple carbohydrates and free sugar, I came across an article about testing your personal carbohydrate tolerance based on a simple test devised by Dr Sharon Moalem in his book : "The DNA Restart".  For this test you need an unsalted cracker biscuit (e.g. a small water biscuit or half of a cream cracker) and a stopwatch.  Place the cracker in your mouth, start the watch, and begin chewing the cracker without swallowing it.   Continue chewing until the cracker begins to taste sweet and note the time.  If you have noticed no change after 30 seconds then stop the test.


If you notice a change in under 14 seconds then your recommended carbohydrate consumption is classified as Full; 15 to 30 seconds is Moderate, while more than 30 seconds is Restricted.   Dr Moalem then recommends the following approximate guide levels of carbohydrate consumption for each category :


Carbohydrate tolerance

Carb intake for women

Carb intake for men

% of carb intake















The taste change comes about because we release the enzyme amylase in our saliva to begin the digestion of starch as we chew, but not everyone produces the same amount of salivary amylase.   Those who produce a lot of amylase will experience the sweetness much earlier than someone who produces only a small amount because they begin to pre-digest the starch almost immediately which breaks the food down into simple sugars long before it reaches the small intestine.  You might think from this that someone with a lot of salivary amylase will tend to have greater spikes in blood sugar than someone who does not, as they are generating simple sugars more rapidly.   However the opposite is actually true as the rapid release of sugars triggers an earlier release of insulin which results in better overall control of blood glucose in those blessed with higher salivary amylase.   There is not a full understanding of the actual mechanism but it seems from clinical trials that low salivary amylase is associated with obesity, metabolic syndrome, diabetes, and a BMI typically two units higher than the average.


My amylase cracker test indicated no change in sweetness after 30 seconds so, by Dr Moalem's definition, I have low carbohydrate tolerance and am definitely in the Restricted category of carbohydrate consumption.   That means that I should aim to eat less than 165g of carbohydrate per day.  This would appear to confirm what I discovered by chance during my diet when I cut out all sugar and simple carbs during the weight loss phase and dropped my carbohydrate intake from about 365g down to about 135g per day.  The immediate result, in spite of being calorie constricted, was a huge increase in energy levels which only crashed afer a brief return to eating simple carbs again overthe Christmas period.   Currently I am not calorie restricted but I still avoid simple carbs and sugar.  My intake of "slow" carbs is actually about 160g per day and my energy levels remain high, much higher than when I started this dietary change six months ago.  So maybe it is worth grabbing a cracker to try this simple test before you start dieting to see how carbohydrate tolerant you might be.  Cutting carbs worked wonders for me but that might do it for everyone. 


Here are some background papers on this phenomenon :