What Your CGM Is Actually Telling You: A Blood Sugar Masterclass for Women 40+
Hormones after 40 change everything—especially how your body handles blood sugar and stores fat. If your usual routine isn't cutting it anymore, tracking your glucose might be the missing piece. You don't need diabetes to benefit from a Continuous Glucose Monitor (CGM). That tiny sensor on the back of your arm acts as a real-time metabolic window, revealing exactly how your meals, stress, sleep, and cycle impact your energy around the clock.
I personally have tried the FreeStyle Libre 3 and love me some health data, but after looking at the charts, spikes and dips, I really had no clue what I was looking at. On the latest episode of Fuel with Erin, functional dietitian Kayla Girgen, RD, joined me to share how it can be a great tool for women without diabetes to better understand their bodies and nutrition. This blog posts recaps the highlights from our convo and the full episode is available to view as well.
What a CGM Actually Measures
"A CGM is a continuous glucose monitor," Kayla explained. "So if you've seen people walking around with a little device on the back of their arm, essentially that's measuring their blood sugar in real time and sending that information to an app on your phone." Simple enough. The harder part is understanding what the resulting graph is trying to tell you — and that starts with insulin resistance, a term most women have heard but few can actually explain.
Kayla's analogy is the clearest one we've heard: "It's not that insulin isn't there and doing its job — it's that your cells become tone-deaf to it. I like to explain it like it's a locking mechanism that isn't working, or the keys are a little sticky." Insulin is still showing up to unlock your cells and let glucose in for energy. The lock has just gotten harder to turn. She also points out a real gap in how this gets diagnosed in standard medical care: "What really gets to me is in our medical system, we're diagnosing things like prediabetes and type 2 diabetes strictly off of glucose — we don't unfortunately have a continuous insulin monitor." In other words, the tool that would show insulin resistance developing early simply doesn't exist yet at a consumer level, which is part of why so many women don't find out until things have progressed further than they'd like.
Reading the Graph: Rolling Hills, Not Mountain Peaks
Once the sensor is on, the next question is what a "good" graph even looks like — and Kayla's answer surprises people who assume the goal is a flat line. "The goal is not to have a flat line for your glucose," she said. "Think rolling hills versus mountain peaks." Some rise and fall after eating is completely normal and expected. What you're watching for is the shape and the recovery: "When I see somebody's blood sugar jump up and stay high, that tells me there's likely some insulin resistance. It almost looks like a ledge. Ideally you're coming back to that baseline within two to three hours." For anyone just starting to look at their own data, Kayla suggests using roughly 70 to 140 mg/dL as a general target range.
The Protein-and-Fat Buffer (and a Cold Stone Experiment)
The most actionable piece of the conversation is also the simplest: pair your carbs with something else. "If you were to take anything away from us working together," Kayla said, "it's just — don't have your carbs by themselves." Protein and fat slow digestion and blunt the spike a carb-only snack or meal would otherwise cause.
The first time I put on a CGM, we had dinner and then went to ice cream afterwards, and I was so excited to see how high we can spike it with Cold Stone. And it was barely a blip, because I'd had protein, fats, and healthy carbs in dinner all together." Kayla wasn't surprised: "Ice cream always surprises people, because they think it's gonna go sky high — but there's a lot of fat and cream in there, and that's a good showcase of how fat can be a great buffer." The lesson isn't "eat ice cream freely" — it's that what surrounds a carb matters as much as the carb itself.
The same logic applies to meal timing and frequency, an area where Kayla says people often over-correct. "Eating less often doesn't mean eating less food," she noted — snacking constantly on small amounts isn't automatically better for blood sugar than eating satisfying, well-composed meals less frequently.
When Stress Is the Bigger Spike Than the Meal
Perhaps the most useful reframe in the whole conversation: your nervous system can move your blood sugar more than your fork does. Kayla shared a client story that makes the point vividly. "I got a text from a client — 'look what happened to my blood sugar during this meeting' — it was twice as high as anything she had eaten that day." The mechanism is physiological, not psychological: "When cortisol is high, that's causing your liver to dump glucose, because your body doesn't know that you're preparing for a stressful meeting instead of running from danger. And on top of that, when cortisol is high, that makes you more insulin resistant."
This is exactly why a CGM can be a useful diagnostic tool beyond food tracking alone. As Kayla put it: "We can count carbs, we can count calories, but you can't really quantify your stress — unless you're seeing it on something like a CGM."
The Takeaway
You don't need to obsess over a flat line, panic at every spike, or overhaul your entire diet to get value from understanding your blood sugar. Start with the basics Kayla laid out: pair carbs with protein and fat, don't mistake more frequent eating for better eating, watch for graphs that spike and stay elevated rather than recovering within a couple of hours, and pay attention to how much your stress — not just your meals — might be driving the pattern you're seeing.
Hear the full conversation with Kayla Girgen — including Erin's own CGM data walkthrough and her experience being told by a doctor "we don't have a pill for that" — on the Fuel with Erin podcast. Grab Kayla's free CGM guide at go.kaylagirgenrd.com/cgm-guide.
