Stanford Study Documents Abnormal Glucose Spikes in ‘Healthy’ People

This week Stanford University published a study which substantiates the huge glucose spikes that “healthy” people with normal blood sugar levels experience and that Dr. Joseph Kraft began documenting 45 years ago [2,3,4] — until just before his death in 2017 [5].  To those of us that are familiar with the research of Dr. Kraft, this is a bit like the 1969 Apollo 11 lunar astronauts ‘discovering’ the existence of craters and mountains on the moon that were documented by Galileo in 1609.

Kraft called these abnormal glucose spikes along with the corresponding abnormal spikes of insulin ‘occult diabetes‘ or ‘diabetes in situ‘ [4] and used the term ‘occult diabetes’ to describe it since ‘occult’ in this context means “not accompanied by readily discernible signs or symptoms“.  It is these ‘covert’ glucose spikes that Stanford university researchers reported this week.

The Stanford Study

Stanford researchers gave 57 healthy subjects without prior diagnosis of diabetes continuous glucose monitors (CGM) that recorded their blood sugar fluctuations in their normal environment for two weeks. There were 32 women, 25 men — ranging in age from 25 to 76, with an average age of 51 years [1].

Subject’s Blood Sugar Upon Screening

Upon screening for the study, 5 of the subjects were discovered to have met criteria for having type 2 diabetes, as defined as HbA1c ≥6.5%, fasting blood glucose ≥ 126 mg/dL (7.0 mmol/L), or 2-hour glucose during 75 gram Oral Glucose Tolerance Test (OGTT) ≥ 200 mg/dL (11.1 mmol/L); 14 subjects were found to meet the criteria for prediabetes, defined as HbA1c > 5.7% and < 6.5%, fasting blood glucose 100—125 mg/dL (5.5 mmol/l-6.9 mmol/L) , or 2-hour glucose during OGTT 140—199 mg/dL (7.8-11.0 mmol/L). The remaining 38 subjects had normal blood glucose defined as fasting and 2-hour OGTT plasma glucose and HbA1c below the diagnostic thresholds for prediabetes and diabetes. Average fasting glucose was 93 mg/dL (5.2 mmol/L), 2-hour glucose 125 mg/dL (6.9 mmol/L) and HbA1c 5.4%[1].

Huge Variations in Blood Sugar Response

Researchers found that there was huge inter-individual (between individuals) and intra-individual (in the same individual at different times) variation in blood sugar response which is exactly what a 2015 Israeli study that fitted 800 people with CGMs reported [6]. In light of only the glucose part of Kraft’s findings as well as the data from the Israeli study with a study population more than 10x the size, the Stanford findings are not ‘new’.

Using mathematical techniques including spectral clustering and dynamic time warping, researchers defined 3 clusters of glucose patterns which were said to capture 73% of the variation [1]. Based on the amount of variability in glucose levels in each cluster, researchers classified the 3 patterns as low, moderate and severe variability.

Some People had lots of Abnormal Glucose “Spikes”

The researchers found that each of the 3 patterns showed a progressive increase in both the severity and magnitude of the blood sugar fluctuations. As well, some subjects mainly stayed in the low variability range, whereas others were mostly in the moderate to severe variability range. These are basically rankings of blood sugar “spike” intensity [7].

Of significance, blood sugar in the individuals that were considered healthy fluctuated a lot more than what is normally picked up by standard ‘finger-prick’ methods of blood sugar testing and these fluctuations come in the form of “spikes’; which are rapid increases in the amount of glucose (sugar) in the blood, especially after eating specific foods — most commonly carbohydrate [7].

Dr. Michael Snyder, professor and chair of genetics at Stanford and senior author of the study said;

“There are lots of folks running around with their glucose levels spiking, and they don’t even know it. The covert spikes are a problem because high blood sugar levels, especially when prolonged can contribute to cardiovascular disease risk and a person’s tendencies to develop insulin resistance, which is a common precursor to diabetes.”

“We saw that some folks who think they’re healthy actually are misregulating glucose—sometimes at the same severity of people with diabetes—and they have no idea [7].”
~ Dr. Michael Snyder

Stanford researchers documented that abnormal glucose responses were more common than they previously thought [7], but these results come as no surprise to those of us familiar with Kraft’s research [2-5] and the findings of the 2015 study from Israel [6].

You can read more about the significance of these covert glucose and corresponding insulin spikes in this article titled When Normal Fasting Blood Glucose Results Aren’t Necessarily “Fine”.

Cornflakes For Breakfast?

The Stanford researchers conducted a sub-study in 30 subjects whose prior blood sugar tests indicated that they were “healthy” (i.e. not prediabetic or diabetic). They were fitted with continuous glucose monitors (CGMs) and alternated between 3 breakfasts; (1) a bowl of cornflakes with milk, (2) a peanut butter sandwich and (3) a protein bar.

Significantly, more than half of the “healthy” group had blood sugar spikes at the same high levels as those who were diagnosed as prediabetic or diabetic  [1,7].

Dr. Michael Snyder, professor and senior author of the study said;

“We saw that 80% of our participants spiked after eating a bowl of cornflakes and milk. Make of that what you will, but my own personal belief is it’s probably not such a great thing for everyone to be eating[7].”

Ordinary Blood Tests Available to Detect These Abnormal “Spikes”

Different people respond to carbohydrate based foods differently and even the same individual can respond to the same carbohydrate-based food differently — depending on part on the degree of processing it has undergone, or whether it is eaten alone or after eating protein-containing foods (see two articles on the Perils of Food Processing for more information).

As elaborated on in a previous article titled “Are You Pushing Your Pancreas Too Hard, abnormalities in insulin, including insulin resistance and/or hyperinsulinemia begin to occur as much as 20 years before a diagnosis of Type 2 Diabetes [8]; while blood sugar results are still normal and the results of this new Stanford study underscores the need to diagnose these abnormalities by capturing the blood glucose and insulin spikes well in advance of that!

The problem is, if we only monitor people’s fasting blood glucose and glycated hemoglobin (HbA1C) as a screening tool, we can miss that someone’s pancreas is overworking by constantly producing too much insulin.

Even if a standard 2 hour Oral Glucose Tolerance Test (OGTT) is run, if a person’s blood glucose results are normal at fasting and normal at 2 hours (such as was the case in the Stanford study!), we will miss the “spike” that occurs 30 minutes to 1 hour after the glucose is consumed in those with covert glucose spikes. The way to capture those “spikes” is to run a 2 hour Oral Glucose Tolerance Test with simultaneous glucose and insulin and do the two measurements at baseline (fasting), 30 minutes / 1 hour, and at 2 hours. When we detect these “spikes”, we can implement dietary changes to avoid further β-cell damage or β-cell death whose end-result is type 2 diabetes.

The Cost of Documenting These “Spikes” – penny wise and pound foolish

For less than $130 (cost in British Columbia, Canada), a physician can order a 2-hour OGTT with both glucose and insulin measured at (a) fasting, (b) 1 hour and (2) 2 hours which will capture abnormal glucose spikes at 1 hour, as well as the underlying hyperinsulinemia.

When there are clinical reasons to suspect that a person may be insulin resistant and/or hyperinsulinemic, a blood test that assesses simultaneous glucose and insulin response to a glucose challenge can provide sufficient motivation for individuals to implement dietary changes that can prevent progression to Type 2 Diabetes.

is such a test that costs <$130 to the public healthcare system not good value when the cost per person per year of having Type 2 Diabetes in Canada ranges from $1611 to $3427 ( more about that here)?

In British Columbia, the cost of a standard 2 hour Oral Glucose Tolerance Test is $11.82 before tax and $13.36 with HST.

Each additional glucose assessment is $3.48 before tax and $3.93 after tax.

Each insulin assessment costs $32.82 before tax and $37.09 after tax, so a 2 hour Oral Glucose Tolerance Test with additional glucose assessor at 1 hour and 3 insulin assessors at fasting, 1 hour and 2 hour costs as follows;

2 hour Oral Glucose Tolerance (fasting, 2 hours)           = $  13.36  with GST
additional glucose at 1 hour                                                       = $   3.93   with GST
3 insulin assessors at fasting, 1 hour, 2 hours                   = $111.27  with GST
TOTAL                                                                                                   = $128.56 with GST

The reason often given by physicians for NOT requisition the above tests is that it is “saving healthcare system dollars”, but in those with clear risk indicators, how is it wise to ignore what can’t be detected with standard screening tests?

More Info?

If you would like more information about determining how you respond to carbohydrate containing foods and whether you are at risk for prediabetes type 2 diabetes especially if your blood sugar values appear normal on standard screening tests, I can help.

You can learn more about my services under the Services tab or in the Shop.

If you have questions, please feel free to send me a note using the Contact Me form above and I will reply as soon as I can.

To your good health!


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Copyright ©2019 The Low Carb Healthy Fat Dietitian (a division of BetterByDesign Nutrition Ltd.)

LEGAL NOTICE: The contents of this blog, including text, images and cited statistics as well as all other material contained here (the ”content”) are for information purposes only.  The content is not intended to be a substitute for professional advice, medical diagnosis and/or treatment and is not suitable for self-administration without the knowledge of your physician and regular monitoring by your physician. Do not disregard medical advice and always consult your physician with any questions you may have regarding a medical condition or before implementing anything  you have read or heard in our content.


  1. Hall H, Perelman D, Breschi A, et al, 2018, Glucotypes reveal new patterns of glucose dysregulation. PLOS Biology 16(7).
  2. Kraft JR, Glucose Insulin Tolerance. A routine Clinical Laboratory Tool Enhancing Diabetes Detection. In O.B. Hunter. Jr. (ed): Radio assay: Clinical Concepts. Skokie, IL. Professional Education Dept. G.D. Searie & Co., 1974. Pp 91-106.
  3. Kraft JR, The Glucose Tolerance Examination: An Obsolete Procedure. read at the Symposium on Radioimmunioassay in Diagnostic Medicine.” Annual Convention, American Medical Association, Chicago, IL. June 26, 1974
  4. Kraft JR, Detection of Diabetes Mellitus In Situ (Occult Diabetes), Laboratory Medicine, Volume 6, Issue 2, 1 February 1975, Pages 10—22,
  5. Crofts C, Schofield G, Zinn C, Wheldon M, Kraft J., Identifying hyperinsulinaemia in the absence of impaired glucose tolerance: An examination of the Kraft database. Diabetes Res Clin Pract, 2016. 118: p. 50-7.
  6. Zeevi D, Korem T, Zmora N, et al. Personalized Nutrition by Prediction of Glycemic Responses. Cell. 2015 Nov 19;163(5):1079-1094.
  7. Medical Press, July 24, 2018, Diabetic-level glucose spikes seen in healthy people, study finds,
  8. Sagesaka H, S.Y., Someya Y, et al, Type 2 Diabetes: When Does It Start? Journal of the Endocrine Society, 2018. 2(5): p. 476-484.

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