My point being in this instance however that the glucose reading indicated by the poster suggested that a late night high carb treat might be acceptable due to the fact that they were not aware of the considerable spike they likely had while sleeping, causing a larger than usual insulin response that resulted in a deceptively lower than usual glucose reading the following morning.
I am not suggesting that glucose readings are unreliable, but that there are a number of factors in how the human body behaves that can cause readings to fluctuate this way or that in the course of a day that can create incorrect perceptions that suggest such a late night high carb treat might well be acceptable.
Having experimented with such increases in carb intake myself in a similar manner with the end result being an increase in my hba1c, I can assure them that such treats on a regular basis while having the appearance of being acceptable according to daily glucose readings, will with certainty result in an increased hba1c. Thus the hba1c is the truer indicator of what his blood glucose readings are over the longer period.
What I am also suggesting is that where one is consistently staying true to a low carb diet, that while there may be fluctuations in glucose readings in the course of a day that suggest things may or may not be well, that over the longer term by staying true to the diet, they will generally see a stabilised and/or improved hba1c and also improvement in general health.
Thus my directive was to steer them towards fats rather than carbs to satiate the appetite they had been experiencing, as such a course of action will help reverse the old habit and introduce one that has a more positive impact on the blood glucose over the longer term. Again, I have tested this on myself, it works!