Part 7: Wearing a Continuous Glucose Monitor as a non-diabetic Physician: What the literature says about responses to carbohydrates in a fat-adapted human

2018.05 Low Carb and Low Carbon - Ted Eytan MD.001-546
2018.05 Low Carb and Low Carbon – Ted Eytan MD.001-546 (View on Flickr.com)

As I mentioned in part 6 of this series, for a person without known diabetes/prediabetes, the readings from a Continuous Glucose Monitor (CGM) are going to mostly be flat (the incredible ability of our bodies to regulate themselves).

As other research has shown (see: Just Read: New Insights into Glucose Dysregulation from Continuous Glucose Monitoring & Foods Most Recommended for Reversing Prediabetes Seem to Have Greatest Potential to Cause Prediabetes), a CGM can show early signs of the breakdown of the regulation system.

I have also been told that people who are fat-adapted (eating a low-carbohydrate, healthy fat diet or LCHF) should not do glucose tolerance tests unless they carbohydrate load. On two (actually three) occasions I did this, and while I didn’t veer into pre-diabetes territory, I was curious as to this statement and the mechanism, so I found this paper:

Kinzig KP, Honors MA, Hargrave SL. Insulin sensitivity and glucose tolerance are altered by maintenance on a ketogenic diet. Endocrinology [Internet]. The Endocrine Society; 2010 Jul [cited 2018 Oct 10];151(7):3105–14. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20427477

Unfortunately, it’s a rat study

This limits the interpretation in my mind, since many rat studies have not been shown to correlate to human biology.

Unfortunately, the rats fed a low-carbohydrate diet were not fed healthy fats (Lard: healthy, Soybean oil: not-healthy)

The sources of fat in KD (ketogenic diet) were soybean oil and lard, such that the diet was composed of saturated and unsaturated long-chain fatty acids.Kinzig KP, Honors MA, Hargrave SL. Insulin sensitivity and glucose tolerance are altered by maintenance on a ketogenic diet. Endocrinology [Internet]. The Endocrine Society; 2010 Jul [cited 2018 Oct 10];151(7):3105–14. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20427477

Rats on an LCHF diet may secrete more insulin when exposed to high carbohydrates

KD rats had significantly greater insulin levels in response to a glucose challenge than did chow-fed controls, although blood glucose levels were indistinguishable between dietary groups. As such, it appears that long-term maintenance on the KD may lead to resistance to peripheral insulin over time. One possibility is that decreased exposure to dietary carbohydrates may render one unprepared to mount an appropriate physiological response to an insulin or glucose challenge. The malleability of this effect is demonstrated by the normalization of insulin and glucose responses to a glucose challenge 1 wk after ceasing ingestion of the KD and resuming maintenance on chow.Kinzig KP, Honors MA, Hargrave SL. Insulin sensitivity and glucose tolerance are altered by maintenance on a ketogenic diet. Endocrinology [Internet]. The Endocrine Society; 2010 Jul [cited 2018 Oct 10];151(7):3105–14. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20427477

This is not necessarily a bad thing, as

  • this type insulin resistance reverses upon resumption of a high carbohydrate diet
  • it may be more physiological than pathological, a normal response to muscles not requiring glucose from the bloodstream as much when they are not continually flooded
  • it’s better to have a stable glucose level than an unstable one that comes from chronic ingestion of carbohydrates and industrial vegetable oils, so this finding does not support going to the Standard American Diet (SAD)

All of this could explain the sustained hypo/very hypoglycemia I experienced after a carbohydrate challenge on an empty stomach

2018.10.07 Low Carb and Low Carbon 550
2018.10.07 Low Carb and Low Carbon 550 (View on Flickr.com)

In a person who is not diabetic and specifically not type 1 diabetic and therefore produces insulin, this is not as dangerous as it would be for someone who does not produce insulin.

In the image at the very top of this post, the carbohydrates were limited and not ingested on an empty stomach, so it’s possible that the healthy fat in the meal preceeding acted as a buffer and didn’t expose the body to the full brunt of the carbohydrate load all at once.

Rats on an LCHF diet also have greater brain receptors for insulin, protective for hyperphagia (overeating)

We demonstrate that maintenance on a KD results in increased sensitivity to the anorectic effects of central insulin and is likely involved in mediating the lack of hyperphagia that is commonly observed in the presence of low systemic insulin.Kinzig KP, Honors MA, Hargrave SL. Insulin sensitivity and glucose tolerance are altered by maintenance on a ketogenic diet. Endocrinology [Internet]. The Endocrine Society; 2010 Jul [cited 2018 Oct 10];151(7):3105–14. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20427477

This may also relate to what’s being discovered about dementia and the role of insulin resistance (see: Just Read: Alzheimer’s Disease Is Type 3 Diabetes—Evidence Reviewed

A Desire to Know, in the interest of better health

As more data comes out about the responses of physiologically normal people to changes in diet as shown via CGM, we’ll more able to expect the expected rather than consider the unknown “pathological” without investigation. I’ll be posting more data and literature related to it in the next few weeks.

Experience is the best teacher and the most potent stimulator of curiosity 🙂

Comments and checking of my work welcome; please post in the comments.

Disclaimer and this is not a promotion of CGM-for-all

I’ve been asked directly or indirectly recently if I am advocating CGM-for-all. I am not, and definitely not with the current profile of devices available. This could change dramatically if CGM is more universally available (see blog posts above).

Reminder of my statement of independence and no conflict-of-interest:

2018.05.29 Low Carbohydrate Meetup Washington, DC Presentation  453
2018.05.29 Low Carbohydrate Meetup Washington, DC Presentation 453 (View on Flickr.com)

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