Understanding Blood Sugar: Lessons from My Continuous Glucose Monitor

I wore a continuous glucose monitor for 30 days and discovered some surprising things about how different foods affected my blood sugar levels. What started as a curiosity about my metabolic health turned into a fascinating experiment that changed how I think about nutrition and wellness.

The continuous glucose monitor (CGM) technology was originally developed for people with diabetes to track their blood sugar levels in real-time. However, they're increasingly being used by health enthusiasts like me who want to understand their metabolic responses to different foods, exercise, stress, and sleep.

Why I Decided to Try a CGM

Over the past few years, I've become increasingly interested in metabolic health and its connection to overall wellness. We often hear about how certain foods spike blood sugar and how these spikes can lead to energy crashes, increased hunger, and potentially contribute to long-term health issues.

I wanted to see beyond generalized nutrition advice and understand how my unique body responds to different foods and lifestyle factors. Was my morning oatmeal causing the mid-morning energy dip I often experienced? Did my afternoon workout improve my glucose regulation? How did stress and sleep affect my metabolic function?

After researching the available options, I chose a CGM system that's available without a prescription and wore it for 30 days. The sensor was applied to the back of my arm and continuously monitored my interstitial glucose levels, sending the data to my smartphone.

My Most Surprising Discoveries

1. "Healthy" Foods Weren't Always Metabolically Friendly

One of my biggest shocks was seeing how some foods I considered healthy caused significant blood sugar spikes:

• Smoothies: My morning "green" smoothie with banana, berries, spinach, and a touch of honey caused one of my highest glucose spikes of the experiment. Even though it contained fiber and nutrients, the blended fruit sugars hit my system quickly.
• Brown rice: This supposed health food gave me a higher spike than white pasta, which was unexpected.
• Oatmeal: My typical breakfast of steel-cut oats with fruit caused moderate to high spikes, explaining my mid-morning energy crashes.
• Certain fruits: Bananas and grapes caused substantial spikes when eaten alone, while berries and apples had much gentler effects.

2. Food Combinations Matter Tremendously

I discovered that how I combined foods made a significant difference:

• Adding protein and fat to carbohydrates dramatically reduced glucose spikes
• Eating vegetables before carbohydrates blunted the subsequent glucose response
• A tablespoon of apple cider vinegar in water before carb-heavy meals reduced spikes by about 20% on average

For example, when I ate a slice of sourdough bread alone, my blood sugar rose significantly. But when I had the same bread with avocado, eggs, and a side of sautéed spinach, my glucose response was much more gradual and controlled.

3. Timing Made a Significant Difference

I found that my glucose response to the exact same meal varied based on timing:

• Morning carbohydrates caused higher spikes than the same foods eaten later in the day
• Eating my largest meal at lunch rather than dinner resulted in better overall glucose patterns
• Late-night eating (after 8 PM) led to higher and more prolonged glucose elevations compared to eating the same food earlier

4. Exercise Was Powerfully Effective

Physical activity had a remarkable effect on my blood sugar:

• A 15-minute walk after meals reduced post-meal glucose spikes by 30-40%
• Strength training improved my glucose regulation for up to 36 hours
• High-intensity interval training had the most dramatic and longest-lasting effects on improving my insulin sensitivity

On one occasion, I ate a higher-carb meal and then couldn't take my usual post-meal walk due to a work call. My glucose spiked over 160 mg/dL. The next day, I ate the same meal but took a 15-minute walk immediately after, and my peak was only 125 mg/dL - a significant difference!

5. Stress and Sleep Were Massive Factors

Non-food factors had surprisingly strong effects:

• A night of poor sleep (less than 6 hours) resulted in glucose spikes 20-30% higher the next day, even with identical foods
• Work stress visibly raised my baseline glucose levels and led to higher spikes
• Meditation and deep breathing practices before meals seemed to improve my postprandial (after-meal) glucose responses

Key Lessons for Metabolic Health

After analyzing a month of data and over 90 meals, here are the patterns I found most valuable:

Focus on Food Order

Starting meals with fiber, protein, and healthy fats before consuming carbohydrates made a consistent difference in glucose response. I began adopting a simple meal structure:

1. Non-starchy vegetables first (leafy greens, broccoli, etc.)
2. Protein and healthy fats second (eggs, fish, nuts, avocado, olive oil)
3. Starchy or higher-carb foods last (grains, potatoes, fruit)

This simple change reduced my average glucose spike by about 25% compared to eating the same foods in random order.

Movement Is Medicine

The data made it clear that consistent movement throughout the day was more important than occasional intense exercise for glucose regulation. I implemented:

• A minimum 10-minute walk after each meal
• "Movement snacks" - 2-3 minutes of squats, push-ups, or stretching every hour during workdays
• Standing rather than sitting when possible

Individualize Your Diet

Perhaps most importantly, I learned that general nutrition recommendations don't always apply to individual metabolism. Foods that were supposed to be "healthy" sometimes didn't work well for my body, while others that are often demonized caused minimal issues.

For example, I found that:

• Sweet potatoes gave me better glucose responses than white potatoes
• Basmati rice caused smaller spikes than brown rice
• Sourdough bread was better for my glucose levels than whole wheat bread
• Whole fruit with plain yogurt created minimal spikes compared to smoothies

Changes I've Made Based on My CGM Data

After completing my 30-day experiment, I've implemented several sustainable changes to my daily routine:

Breakfast Redesign

I switched from oatmeal and fruit to a protein-forward breakfast of eggs with avocado and vegetables. On days when I want something sweet, I have Greek yogurt with a small amount of berries and nuts, which gives me sustained energy without the mid-morning crash.

Meal Sequencing

I now start most meals with non-starchy vegetables and protein before consuming any carbohydrates. This simple change has made a remarkable difference in my post-meal energy levels.

Strategic Movement

I've built short walks into my daily routine, particularly after meals. Even just 10 minutes of movement has proven effective for glucose management.

Mindful Carbohydrate Consumption

Rather than avoiding carbs entirely, I'm more intentional about:

• When I eat them (preferably at lunch rather than breakfast or late dinner)
• What I pair them with (always with protein, fiber, and healthy fats)
• Portion sizes (smaller amounts of carbohydrates lead to more manageable glucose responses)

Stress Management

Seeing the concrete impact of stress on my glucose readings motivated me to prioritize stress-reduction techniques, including a brief meditation practice before meals and better boundaries around work hours.

Is a CGM Worth It?

For me, the month-long CGM experiment was eye-opening and well worth the investment. It helped me understand my body's responses in a way that no generic nutrition advice could provide. That said, it's important to note:

• CGMs can be expensive and typically aren't covered by insurance for non-diabetic individuals
• The data requires thoughtful interpretation and experimentation
• It's possible to become overly focused on glucose numbers rather than overall health

If you're curious about your metabolic health but not ready to try a CGM, you can still apply many of the principles I discovered:

• Start meals with vegetables, protein, and healthy fats
• Take short walks after eating, especially after higher-carb meals
• Pay attention to how different foods affect your energy and hunger levels
• Prioritize quality sleep and stress management

Have you tried a continuous glucose monitor or made changes to your diet based on how foods affect your energy levels? I'd love to hear about your experiences in the comments below.