Beyond the Scale: What You Should Know About CGMs and Your Low Carb Lifestyle

But now, you may have seen a lot of people without diabetes, including celebrities and influencers, as well as low-carb eaters, who are using them to track how their bodies respond to food, stress, sleep and even exercise. Here’s what else you need to know about CGMs and whether one may be right for you.

For the low carb crowd, CGMs can be eye-opening. They can reveal if you’re experiencing blood sugar spikes from so-called healthy foods, like smoothies, fruit-flavored yogurt, certain grains or natural sweeteners. You may learn how different carbs affect you, such as oatmeal or roasted sweet potatoes, or foods with healthy fats and protein that may still be high in hidden carbs, like breaded and fried proteins. You may discover how tweaking your meal timing, meal sequencing or exercise can help stabilize your blood sugar and help eliminate cravings or how exercise intensity, hydration, stress, poor sleep, illness or infection affect your glucose levels. Because weight management and a reduced risk of chronic disease are the long-term benefits of stable blood sugar, this information can be quite valuable.

Even if your fasting levels are considered optimal, you may still experience daily blood sugar spikes. A blood sugar spike occurs when glucose is delivered to cells too quickly, prompting your pancreas to release insulin into your system to bring your levels back down. When these spikes are frequent and severe, your cells can become less responsive to insulin’s signal, known as insulin resistance. This means your body needs to produce even more insulin to do the same job, creating a vicious cycle where both glucose and insulin levels remain elevated. Too much glucose accumulating in your bloodstream, coupled with high insulin levels, causes oxidative stress, a type of cellular damage that acts as a major driver for serious chronic diseases, including heart disease, type-2 diabetes and cognitive decline like Alzheimer’s, along with contributing to accelerated weight gain and aging. The immediate aftermath also can include energy crashes, persistent cravings and difficulty managing hunger. And some spikes are worse than others. For example, the sharp, rapid blood sugar spike you experience after eating a cupcake (high in refined sugars and low in fiber) is far more impactful and damaging than a more tempered spike you might see after eating a piece of whole-wheat bread, where the fiber helps moderate glucose absorption.

Typical healthy fasting blood sugar levels for non-diabetics (before meals, especially in the morning) are 70-99 mg/dL (3.9-5.5 mmol/L), although many health professionals suggest an optimal fasting range might be closer to 72-90 mg/dL.

Blood sugar will naturally rise as glucose enters your bloodstream. For a healthy person, this usually happens around 60 to 90 minutes after a meal. The peak level should generally remain below 140 mg/dL.
Many studies with CGMs in healthy people show post-meal peaks often stay under 110 mg/dL, especially when eating balanced meals. Blood sugar levels typically return to pre-meal levels within two to three hours after eating.

Overall, a healthy non-diabetic typically maintains their glucose levels between 70-140 mg/dL (3.9-7.8 mmol/L) for most of the day (e.g., 90-96% of the time). Brief, transient dips below 70 mg/dL (mild hypoglycemia) or slight rises above 140 mg/dL may occur occasionally, but they should quickly return to normal.

CGMs provide real-time data, which may boost your motivation to increase your activity or improve your food choices when sensors detect a blood sugar spike. CGMs may also help athletes tailor their carb intake for optimal performance or detect early signs of insulin resistance.

There is one caveat, however: CGMs aren’t always accurate if you don’t have diabetes. They may overestimate blood sugar spikes by ~30% compared to standard finger-prick tests. As they measure interstitial fluid (the fluid surrounding your cells), not blood directly, there may be a lag of five to 20 minutes in timing.

It’s also important to note that every bump in your blood sugar isn’t bad, as your blood sugar levels naturally fluctuate throughout the day. Even if you’re considered healthy, it’s not meant to be a flat line. Your body’s sophisticated system of hormones (primarily insulin and glucagon) works to keep these fluctuations in a relatively controlled and healthy range.

With that being said, a CGM may also cause anxiety if you become fixated on the numbers and overreact to normal fluctuations. CGMs may also be expensive and not always covered by insurance.

Before jumping in, ask yourself: Will this help me make sustainable changes, or add to the mental clutter of trying to do everything “perfectly”?

You may not need a fancy device to know that starting your day with eggs and avocado feels better than a bagel. Or that a protein-packed lunch gives you more stamina than a carb-heavy sandwich.

Blood sugar balance isn’t about perfection—it’s about patterns. But, if you love data and feedback, a CGM might help you connect the dots and personalize your low carb journey.