I not sure where this 5.0 is the sweet spot is coming from - other than being influenced by the all cause mortality association U curve studies?
Since you mention Dr Attia, from here he seems to think that lower is better.
Note also that the glucose level of zero is not relevant, because there are so many parts of our biology and hunger drive that will make it difficult to go too low (in a healthy, metabolically fit individual) if one is not overusing medicines.
Peter Attia’s calculation is that 4.6% represents estimated average glucose levels of 85 mg/dL. That does not look like a level that is too low for the liver in a person who is optimized from a metabolic perspective and easily can utilize fat and not just glucose as energy.
From below you can also see that Dr Attia seems quite happy with 4.6
Glucose control lives on a spectrum, but it conventionally gets lumped into three distinct categories: normal glucose tolerance, prediabetes, and diabetes. For example, whether your HbA1c is 4.6% or 5.6%, both are considered “normal” because they both fall under the diagnostic threshold of 5.7%. Once it hits 5.7%, so long as it does not exceed 6.4%, now you’ve got impaired glucose tolerance, also referred to as prediabetes. Once you’ve eclipsed the latter, whether your HbA1c is 6.5% or 12.5% (or even higher), you’re categorized as having type 2 diabetes. In most cases of type 2 diabetes, an individual traverses from one bucket to the next as their HbA1c slowly climbs from normal to impaired to outright diabetic. This doesn’t happen overnight, but too often it’s only confronted when the diabetes or prediabetes threshold is reached at a snapshot in time. Progressing from an HbA1c of 4.6% to 5.6% represents estimated average glucose levels climbing from 85 to 114 mg/dL.
Are continuous glucose monitors a waste of time for people without diabetes?.. 3
And here he gives his view on that lower average glucose is better* and puts that in context of success with a patient who came down to 84 mg/dL and hence at or below a predicted 4.6% HbA1c:
To recap my position and interpretation of the data available (more of which you can find in the AMA 24 show notes), lower is better than higher when it comes to average glucose, glucose variability, and glucose peaks, even in nondiabetics. In other words, there’s a lot of evidence suggesting that people with glucose in the normal range can benefit from lowering their numbers.
Let me give you an anecdote, among several I could share, to demonstrate why I find CGM useful in nondiabetics. I have a patient who came to me with normal glucose tolerance by standard metrics. He began CGM and after about two weeks it revealed an average glucose of 104 mg/dL over that time. The standard deviation in his glucose readings, which is a metric of glucose variability, was 17 mg/dL. He averaged more than five events per week in which his glucose levels exceeded 140 mg/dL. All three of these metrics are considered normal by conventional standards, but does that mean there’s no room for improvement? I like to see my patients with a mean glucose below 100 mg/dL, a glucose variability below 15 mg/dL, and, as noted above, no excursions of glucose above 140 mg/dL. After about a four-week intervention that included exercise changes and nutritional modifications his average glucose fell to 84 mg/dL, his glucose variability to 13 mg/dL, and he had zero events exceeding 140 mg/dL. If he can maintain this way of living in the long-run, it’s likely to translate into an improvement in healthspan and reduce his risk of glucose impairment.
