Are CGMs worth the hype?

>>>Let’s play Lingo!<<<

When I hear “Lingo”, I think of a game show hosted by RuPaul. But lately I’ve been hearing “Lingo”on ads for a continuous glucose monitor (CGM) being marketed to consumers.

CGMs are definitely game-changing technology for people with diabetes who take insulin. Tracking blood sugar levels in real time is crucial for them, and CGMs make it more convenient to do so.

CGMs can be life-changing technology

But the ads would lead you believe that CGMs are useful for non-diabetics as well, by tracking the reaction of blood sugar levels to certain foods. We know that extreme post-meal (aka “postprandial”) blood glucose spikes are linked to a variety of health problems. By monitoring your blood sugar over time, you can see which meals cause the biggest spikes, and make adjustments to your diet, with the goal of improving health & fitness outcomes, and reducing the risk of metabolic disease - at least, that's the theory.

These outcomes rely on a couple of assumptions: that different individuals have different post-meal responses to the same meal on any given day; and that one individual would have similar responses to the same meal on different days.

Put a different way: that your post-meal glucose responses are unique to you; and your unique glucose responses are consistent and reliable.

Unfortunately, a recent study by researchers at the US National Institutes of Health found those assumptions don’t hold up.(1) Study participants (wearing CGMs) lived in a research hospital for two weeks at a time. They were served a total of 21 different meals the first week, and the exact same 21 meals in the second week. In other words, a very controlled environment.

The study found that participants had widely different glucose responses to identical meals – almost as if they had eaten two completely different meals. This backed up results of previous research(2), and sort of takes out the main rationale for using a CGM as a non-diabetic.

Bottom line: Unless you have diabetes, or you’re at high risk, you probably don’t need to monitor your glucose.

Chronically elevated glucose is a hallmark of type 2 diabetes; and high-carbohydrate meals lead to a rise in glucose, which is a problem for diabetics, whose ability to manage glucose is impaired.

This doesn’t mean that normal post-meal glucose elevation causes type 2 diabetes, or that otherwise healthy individuals need to monitor and manage their glucose response.

Understanding the limitations of CGMs is key. CGMs are still a crucial tool for diabetics managing their blood sugar, because it doesn’t matter if their glucose response to a particular meal is different from the last time they had that meal. What matters is knowing their current blood sugar level, and being able to act on it if necessary.

If you’re concerned that you’re at risk, see your doctor for a blood test. With a clinical diagnosis, a CGM could be part of your plan to manage your blood sugar.

If you’re just a data nerd and want to have one more gadget to track your info, know this: your glucose dynamics can vary wildly from day to day, even if you eat the exact same foods; high-intensity exercise will affect your glucose tolerance; and if you generally follow a low-carb diet, an occasional carb-heavy meal could spike your glucose level more than usual. Like any other fitness tracking device, decide how you’re going to use this data in the pursuit of your health and fitness goals.

Or try this low-tech way to minimize post-meal glucose response: eat protein and vegetables at the beginning of a meal, and carbs at the end. A 2015 experiment found participants’ blood sugar level was 29% lower (30 minutes post-meal) with protein/veggie-first meals, compared to identical carb-first meals.(3)

Maybe you don’t need a fancy device at all. Do you really need an external device to tell you that a certain food makes you feel bloated? Or makes you “crash” an hour after eating? Go old school, and journal your responses to different meals and foods. Maybe just being more mindful, and tuning into your body more, will help.

Learn more here: Should people without diabetes use CGMs?

References

1. Hengist, Aaron, Jude Anthony Ong, Katherine McNeel, Juen Guo, and Kevin D. Hall. 2025. “Imprecision Nutrition? Intraindividual Variability of Glucose Responses to Duplicate Presented Meals in Adults without Diabetes.” The American Journal of Clinical Nutrition 121

2. Betts, J. A., and J. T. Gonzalez. 2016. “Personalised Nutrition: What Makes You so Special?” Nutrition Bulletin 41 (4): 353–59.

3. Shukla, Alpana P., Radu G. Iliescu, Catherine E. Thomas, and Louis J. Aronne. 2015. “Food Order Has a Significant Impact on Postprandial Glucose and Insulin Levels.” Diabetes Care 38 (7): e98-9.