I wore a continuous glucose monitor (part 2) before and after keto, here’s what changed…

If you’ve read my earlier blog post about wearing a Continuous Glucose Monitor (CGM), you know I’m a big believer in using data as a learning tool, not something to obsess over.

The first time I wore a CGM was before I was ketogenic. I learned a lot about how my body responded to food timing, stress, hormones, and exercise especially as I was navigating perimenopause.

More than a year later, after becoming keto-adapted and training consistently, I decided to wear a CGM again.

What I saw this time looked completely different, not because my glucose never moved, but because my body handled it faster, smoother, and with far more flexibility.

Disclaimer

This post reflects my personal experience. I am not diagnosing or treating any condition, and this is not medical advice. I do not have diabetes. This is shared purely for education and insight.

Why I Decided to Wear a CGM Again

This second CGM experiment wasn’t about fixing a problem. It was about curiosity.

I wanted to understand:

• how a keto-adapted body handles glucose

• how quickly blood sugar clears now compared to before

• how movement is when insulin sensitivity is high

• how carbs behave when used intentionally

• whether improvements in sleep, stress regulation, and training were showing up metabolically

I already knew what my glucose used to do. I wanted to see what had changed.

The Biggest Difference: Speed

The most striking difference wasn’t the absence of glucose rises, it was how fast everything happened.

Before keto:

• glucose stayed elevated longer after meals

• exercise helped, but gradually

• post-meal walks flattened curves slowly

• glucose clearance often took hours

After keto:

• glucose rises were smaller and smoother

• peaks were often delayed but short-lived

• light movement cleared glucose very quickly

• my body switched back to fat and ketones with ease

In contrast to previous experience, post-meal glucose normalized in minutes, not hours. This is a clear sign of improved insulin sensitivity and metabolic flexibility.

A Real Example: Dinner, Walking, and an Unexpected Lesson

One evening I tested a small amount of Japanese sweet potato at dinner which was about 12 total carbs combined with green beans and avocado.

Roughly an hour later, my CGM showed glucose around 135 mg/dL.

That’s a normal, expected response to a starchy carb, especially in the evening.

Out of habit, I decided to walk on the treadmill while watching TV after eating.

Here’s what surprised me:

• after 18 minutes of easy incline walking, glucose dropped from 135 to the mid-80s

• two minutes later, the CGM showed readings in the 70s

• As my CGM continued to update, it eventually displayed readings below 55 mg/dL. However, when I verified with a finger-stick blood glucose meter, my actual blood glucose was in the high 60s.

I felt completely fine…no shakiness, dizziness, or symptoms.

This discrepancy matters.

CGMs measure glucose in interstitial fluid, not directly in the blood. During movement, rapid glucose clearance, temperature changes, or compression of the sensor, CGMs can read significantly lower than true blood glucose.

This is one of the reasons some CGM devices were pulled from shelves recently not because CGMs aren’t useful, but because inaccurate low readings led people to panic and overcorrect, often with sugar or excess food they didn’t actually need. (You can read the FDA’s recent recall for some devices here.)

In metabolically healthy or keto-adapted individuals, this can be especially misleading:

• glucose may drop quickly during movement

• CGMs may lag or exaggerate the dip

• blood glucose may still be in a safe, functional range

• Without context, this can turn a helpful tool into a source of unnecessary stress.

Finger-stick checks, symptoms (or lack of them), and trend direction matters.

Within minutes of stopping my walk, glucose rebounded on its own, rising smoothly back into the 80s without intervention.

The takeaway?

This wasn’t hypoglycemia. It was efficient glucose disposal.

What used to require longer corrective walks now happens very fast. For someone keto-adapted, more movement isn’t always better, especially at night.

What This CGM Round Taught Me That the First One Didn’t

The first time I wore a CGM, I learned:

• food timing matters

• stress matters

• hormones matter

• not all carbs affect me the same way

This time, I learned something deeper.

1. Keto changes how fast your body responds

• Glucose clearance is quicker.

• Movement is more powerful.

• Overshooting is possible if you overcorrect.

2. CGMs can look “scarier” when you’re metabolically healthy

When your system responds quickly, curves look sharper even though overall control is better.

This is why context matters more than single numbers.

3. Carbs aren’t the enemy, timing is

A small amount of starch at dinner behaves very differently than the same food earlier in the day or paired with training.

4. Data is only helpful if it doesn’t hijack your nervous system

I wasn’t chasing numbers. I wasn’t checking all night. I wasn’t panicking over dips. I used the CGM the way it’s meant to be used: to observe patterns, not create anxiety.

How This Changed (and Confirmed) My Approach to Health

This experience reinforced how I already coach and live:

• lower-carb works best for me overall

• strategic carbs around activity work well

• post-meal movement should be gentle and brief

• more correction isn’t always better

• sleep, stress, and hormones matter as much as food

Most importantly:

A healthy metabolism isn’t fragile…it’s adaptable.