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Introduction
Blood glucose is easy to measure, but not always easy to interpret. This Premium-only episode brings together insights from several previous guests to examine blood glucose responses in more detail.
We discuss the misuse of clinical thresholds, the difference between OGTT results and free-living CGM data, and whether “flatter” glucose curves are actually better in normoglycemic people.
The episode also covers when repeated high glucose excursions may be worth investigating, how sugar intake should be interpreted in context, and why skeletal muscle and exercise play such an important role in glucose regulation.
Overall, the aim is to clarify what glucose responses can tell us, what they cannot tell us, and how to avoid pathologizing normal physiology.
- [02:10] CGMs and misinterpretation
- [04:10] Clinical cutoffs confusion
- [07:32] Three popular claims about glucose variability
- [10:48] Normal glucose regulation
- [18:18] Does variance within normal ranges matter?
- [28:02] When "spikes" might matter
- [33:43] Is sugar uniquely problematic?
- [41:01] Exercise and glucose uptake
Episode Resources
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About the Host
Danny Lennon is the founder of Sigma Nutrition and host of the popular podcast Sigma Nutrition Radio since 2014. Danny has a master’s degree (MSc.) in Nutritional Sciences from University College Cork, in addition to a BSc. Degree in Biology and Physics.
He is the co-creator of the course Applied Nutrition Literacy with Dr. Alan Flanagan.
And he is currently a member of the Advisory Board of the Sports Nutrition Association, the global regulatory body responsible for the standardisation of best practice in the sports nutrition profession.
Study Notes
Useful Terminology
- CGM: Continuous Glucose Monitor. A wearable device that estimates interstitial glucose across the day and displays glucose trends.
- Postprandial Glucose Excursion: The temporary rise in blood glucose after eating, especially after a meal containing digestible carbohydrate.
- Oral Glucose Tolerance Test (OGTT): A standardized clinical test in which a fixed glucose load is consumed and blood glucose is measured at specified time points.
- HbA1c: A marker of average glycemic exposure over the previous several weeks to months.
- Glucose Variability: The degree of fluctuation in glucose over time.
- Hepatic Glucose Output: The release of glucose from the liver into the bloodstream, mainly through glycogen breakdown and gluconeogenesis.
- Gluconeogenesis: The production of glucose from non-carbohydrate substrates.
- Beta-cell Function: The capacity of pancreatic beta cells to secrete insulin appropriately in response to rising glucose. Early impairment in beta-cell function may contribute to abnormal postprandial patterns before standard diagnostic markers become clearly abnormal.
- GLUT4: A glucose transporter found in skeletal muscle and adipose tissue. Insulin and muscle contraction can both promote movement of GLUT4 to the cell surface, allowing glucose to enter the cell.
- Insulin-independent Glucose Uptake: Glucose uptake stimulated by muscle contraction rather than by insulin signaling.
Why CGM Data Are Easy to Misinterpret
Glucose data are now highly accessible, but accessible data are not necessarily intuitive or clinically meaningful. CGMs can show post-meal rises, exercise-related changes, sleep-related changes, and small day-to-day fluctuations. Without context, people may attach diagnostic or moral significance to numbers that reflect normal physiology.
- Blood glucose is a meaningful biomarker, but it becomes problematic when individual readings are interpreted outside the testing context in which clinical thresholds were developed.
- A major source of confusion is the use of diagnostic glucose thresholds from standardized diabetes testing as though they apply to any glucose value observed on a CGM.
- For example, glucose values measured two hours after a standardized OGTT have a specific clinical
