Ahead of the blood sugar curve

Continuous glucose monitoring and the end of an affair

Today, I’m talking about a technology I’ve come to love: Continuous Glucose Monitoring (CGM).

What I love most about CGM is that it gives me lead indicators of my metabolic health and lifestyle choices. Too often, we’re flying blind until a lagging indicator—like unwanted weight gain, hormonal disruptions, or something worse—signals a decline in our health. I’d much rather see where I’m going and course-correct early.

Some other things I love about CGM:

• It’s 10x better than the next best option for understanding my body’s relationship with glucose¹

• It offers fun with data! (optional, if you’re into it)

• Through a clever psychological trick, it nudges me to be healthier—effortlessly

So, without further ado…

What’s Continuous Glucose Monitoring?

CGM helps us observe how our metabolism responds to food and fasting. It involves applying a small sensor to the back of your arm, where a tiny, flexible filament sits just beneath your skin.

CGM in applicator, ready to go. The tiny needle inserted a flexible filament so fast I didn’t feel it

All set to start tracking on the back of my upper arm

This sensor continuously tracks blood sugar levels for up to 14 days, with real-time readings available on your smartphone.

Originally developed for people with diabetes, CGMs are now gaining popularity among non-diabetics who want to optimize metabolic health. They’ve become more accessible as the technology improves and costs decrease.

Using one is easy—DIY, painless, and totally worth it. (I share tips on how to get and use one at the end of this post.)

Why Bother Tracking Blood Sugar?

Metabolic health drives all the major diseases of aging: heart disease, cancer, diabetes, dementia. And since we can have so much influence over our metabolic health, it makes sense to understand it. High blood sugar is one of the five main indicators of poor metabolic health.²

Chronically elevated blood sugar speeds up biological aging, making age-related diseases appear sooner and progress faster.³ Plus, repeated spikes (and the accompanying surges of insulin) contribute to insulin resistance, energy crashes, hunger, overeating, brain fog, and fatigue.

For longevity and vitality, we want stable blood sugar levels—think of a gently undulating bike ride, not a rollercoaster.

How do you see what your blood sugar is doing? A CGM is how.

Since individual responses to food, movement, and sleep vary, getting direct feedback from your own body is incredibly powerful.

What I Learned from Wearing a CGM for 2 Weeks

I’ve worn a CGM twice in the past, each time for two weeks. This time, I was hoping to:

1. See how I measure up against blood glucose guidelines (compared to last time, I’m fitter, eating more protein, and not pregnant).

2. Investigate the blood sugar impact of my dietary “sins” (secretly hoping they’re not too severe so I can keep sinning🤞😈).

Here’s what I found…

Measuring up

I compared my results against two sets of guidance:

• “Not sick”—Standard clinical guidelines aimed at preventing diabetes.

• “Very healthy”—Peter Attia’s stricter thresholds, optimized for healthspan and longevity.

My results consistently fit within the Not sick range but sometimes exceeded Very healthy. Wearing the CGM gave me clear clues on how to improve.

☝️ This is a good table to borrow if you’re thinking of trying a CGM yourself.

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My “sins” 😈

Do my dietary indulgences really mess with my blood sugar? Or can I get away with them? On my list for investigation:

• Skipping breakfast and instead, drinking tea followed by a large oat latte mid-morning

• Snacking frequently once I start eating for the day

• Drinking a glass of wine before dinner (instead of with food)

• Continuing to snack and drink tea (uncaffeinated) after dinner.

Don’t judge me 🫣

Key Takeaways

I could write screeds about everything I learned, but here’s a few highlights:

1. Meals outperformed snacks

Counterintuitively, meals had a more muted impact on my blood sugar than snacks, even when meals were large or snacks were small.

Why?

• My meals typically balance carbs, fat, and protein better than my snack choices

• Snacking (especially before a solid meal) starts me on a blood sugar rollercoaster—spike, crash, repeat.

2. My mid-morning oat latte was a disaster

It sent my blood sugar to the moon… and then straight back down, often into hypoglycemia. I watched this play out daily.

Fiddlesticks. I loved that oat latte.

Switching to decaf didn’t help. Switching from oat to dairy milk did improve things.⁴

Oat milk is an ultra-processed, highly refined, liquified carbohydrate. Honestly, I’m not sure it’s much better than drinking a Coke.

Me and the oat latte? We’ve broken up.

Thanks People’s Coffee for making my last Oat Latte a good one

3. Drinks before dinner?

For those wondering, my pre-dinner glass of wine barely budged my blood sugar. But let’s not kid ourselves—that doesn’t make it a health habit. With food, or not at all, is clearly preferable from a health perspective. A good reminder that blood sugar is just one piece of the puzzle when evaluating our lifestyle choices.

4. Snacking & eating late could be elevating my blood sugar

I suspect my average blood sugar is slightly higher than I’d like because of frequent tea (with milk) and evening snacks.

For example, I noticed that snacking prevented my glucose levels from returning to baseline between meals. And eating late at night shortened my fasting window.

For me, the challenge with these habits is more psychological than nutritional. But I do find the idea of improving my blood sugar levels motivating.

5. Benefits of being watched

The Hawthorne Effect is when we change our behavior simply because we know we’re being observed.

I felt that at work while wearing the CGM. Knowing how the cheese scone would spoil my data somehow dampened its appeal. Even though I’m the only one looking at my data. What a funny creature I am. Fascinating.

Just 2 weeks

So, there are some insights and clues I gathered.

Two weeks wasn’t long enough to draw absolute conclusions about everything. Food, timing, exercise, stress, sleep — there are simply too many variables to isolate.

But it was long enough for me to identify headline metrics and notice what stood out in my daily patterns. Those are the most important things to identify to begin with. It was also interesting to run a couple of psuedo-experiments, to see how I responded to different foods.

My blood sugar is fairly healthy, but there’s room for improvement, and I’ve got solid leads on how to get there.

Every time I wear a CGM, I learn something valuable. I plan to do it again next year. If you’re considering it, even just once in a lifetime is a useful learning experience.

Want to Try a CGM? Here’s What You Need to Know

I use the FreeStyle Libre, mainly because it’s widely available (Dexcom is also a popular option).

• Order it: Online is easiest.

• Cost: About NZ$95 (US$55) for a 14-day sensor.

• Application: Quick, easy, painless. But if you knock it off, you can’t reapply it—annoying! I always wear an adhesive patch over top to keep it secure.

• Don’t buy: A “Reader” for the device, which are sold separately. You don’t need it, provided you have a smartphone.

• Mobile app: Download LibreLink (iOS/Android) for tracking and viewing basic data. Data is pushed automatically to the app, but occasionally loses connection. If that happens you can use your phone to scan the sensor, a bit like Apple Pay — feels weirdly satisfying

• Web app: The LibreView website gives more detailed reports, which are definitely worth reviewing. The interface isn’t winning design awards, but it does the job.

• Logging: You can manually log meals and exercise for extra insights—I didn’t bother doing this very often, but it’s useful.

Go well!

xx Toni

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1. The next best option I’m referring here is an Oral Glucose Tolerance Test, which is the current standard of care for measuring how a person tolerates glucose. I find this test to be frustratingly time consuming, unpleasant, inaccurate and offering no source of insight into causation. Better than nothing though.

2. It’s common to hear metabolic health defined in the negative, as the absence of metabolic syndrome. Metabolic syndrome refers to having three or more of a cluster of related symptoms: High blood sugar, large waistline, elevated blood pressure, high triglycerides, low HDL cholesterol.

3. This is happening through a number of pathways, which are related, for example: inflammation, disrupted metabolism leading to insulin resistance and metabolic syndrome, damage to blood vessels, damage to cells.

4. While dairy may be subject to its own criticisms (environmental, tolerance etc), it is a more natural food. It takes the body longer to convert lactose into glucose and contains protein and fat, all of which serve to moderate glucose absorption. I also found it helped to eat a protein rich breakfast prior to the coffee, but not so much that I wanted to become a regular breakfaster.