Continuous Glucose Monitoring (CGM)

How CGM Works:

A small sensor inserted under the skin measures glucose in interstitial fluid (the fluid between cells). Readings are taken every 1-5 minutes and transmitted wirelessly to a smartphone app.

Key Metrics to Track:

The Glucotype Discovery:

Research has identified distinct "glucotypes" - patterns of glucose response that vary dramatically between individuals: - Low variability: Stable glucose, minimal spikes - Moderate variability: Some meal-related spikes, quick recovery - High variability: Large swings, slow recovery, prediabetic patterns

Roughly 24% of "healthy" non-diabetics show high-variability patterns, spending ~15% of their time above prediabetic thresholds - invisible to standard fasting glucose tests.

What CGM Reveals:

• Personal food responses (rice might spike you but not bread)
• Exercise timing effects (morning vs evening workouts)
• Sleep quality impact (poor sleep = worse glucose control)
• Stress response (cortisol elevates glucose)
• Meal composition effects (protein/fat with carbs blunts spikes)

Why This Matters for Longevity:

Chronic glucose elevations and high variability are associated with: - Increased cardiovascular disease risk - Accelerated aging (glycation of proteins) - Higher inflammation markers - Greater oxidative stress - Increased dementia risk

CGM Protocol:

Phase 1: Discovery (Weeks 1-2)

• Wear CGM continuously
• Eat your normal diet without changes
• Log all meals, exercise, sleep, and stress
• Observe patterns without judgment

Phase 2: Experimentation (Weeks 3-4)

• Test specific foods to find your triggers
• Try meal timing variations
• Test exercise timing effects
• Experiment with food combinations

Phase 3: Optimization (Ongoing)

• Apply learnings to daily life
• Periodic CGM use to verify changes
• Annual or biannual check-ins

Key Experiments to Run:

1. Carb tolerance test: Try 50g carbs from different sources (rice, bread, potato, fruit)
2. Meal order test: Same meal - carbs first vs protein/fat first
3. Exercise timing: Same meal before vs after workout
4. Sleep impact: Compare glucose after good vs poor sleep nights
5. Stress response: Note glucose during stressful periods

Optimal Targets:

• Mean glucose: <100 mg/dL (aim for ~90)
• Standard deviation: <15 mg/dL (aim for ~10)
• Peak: <140 mg/dL (ideally <120)
• No readings above 140 mg/dL

Pro Tips:

• Test foods in isolation first, then in combinations
• Morning glucose responses often differ from evening
• Walking 10-15 minutes after meals significantly blunts spikes
• Protein and fat before carbs reduces glucose response
• Sleep is often the biggest lever for glucose control

Psychological Risks:

• Anxiety/obsession: Constant data can create unhealthy fixation
• Orthorexia trigger: May worsen disordered eating patterns
• Decision paralysis: Too much data can be overwhelming

Who Should Avoid:

• History of eating disorders
• Health anxiety prone individuals
• Those who obsess over metrics

Physical Risks (Minimal):

• Skin irritation at sensor site
• Rare allergic reactions to adhesive
• Minor bruising during insertion

Accuracy Limitations:

• Measures interstitial fluid, not blood glucose (5-15 min lag)
• Less accurate during rapid changes
• Can be affected by pressure on sensor
• First 24 hours often less accurate

Interpretation Cautions:

• Single readings less meaningful than patterns
• "Normal" glucose doesn't mean metabolically healthy
• Context matters (exercise spikes are different from food spikes)

Risk Level: Low physical risk; moderate psychological risk for anxiety-prone individuals

Best Candidates:

• Biohackers wanting personalized metabolic data
• Those with prediabetes or family history of diabetes
• People who've tried "everything" for weight loss
• Athletes optimizing performance nutrition
• Anyone curious about their metabolic response patterns

Good For:

• Learning your personal carb tolerance
• Optimizing meal timing and composition
• Understanding exercise-glucose relationships
• Detecting subclinical metabolic issues
• Data-driven nutrition decisions

Not Recommended For:

• Those with eating disorder history
• People prone to health anxiety
• Anyone who obsesses over numbers
• Those looking for a "magic fix" (it's a learning tool, not treatment)

Best Approach:

Short-term use (1-2 months) for education, then periodic check-ins rather than permanent wear.

Key Metrics to Monitor:

Food Logging Protocol:

• Photo every meal
• Note time, composition, portion size
• Record glucose 1hr and 2hr post-meal
• Rate satiety and energy levels

What Good Data Looks Like:

A well-controlled 24-hour example: - Average: ~90 mg/dL - Standard deviation: 9-10 mg/dL - Peak: 102 mg/dL - Low: 77 mg/dL - Range: 25 mg/dL

Pattern Recognition:

After 2-4 weeks, you should identify: - Your worst spike triggers - Best pre-meal strategies - Optimal exercise timing - Sleep's impact on your control

When to Retest:

• After significant diet changes
• When starting new exercise program
• During stressful life periods
• Annually for metabolic check-in

Compare CGM Services:

See OptimizeBiomarkers CGM Comparison for head-to-head comparisons of Levels, Nutrisense, Signos, and more.

CGM Services (App + Sensors + Insights):

• Levels Health - Best overall experience, comprehensive app, strong educational content, community access. Starting at $199/year + sensors.

• Nutrisense - Includes registered dietitian access, good for those wanting professional guidance. $225-350/month.

• Signos - Weight loss focused, GLP-1-like approach using glucose optimization. $199-399/month.

• Veri - Budget-friendly option, clean app interface. $99-199/month.

Direct CGM Purchase (DIY):

• Dexcom Stelo - First OTC CGM for non-diabetics, ~$99/month for 2 sensors

• Freestyle Libre 3 - Widely available, smaller sensor, 14-day wear. Requires prescription but often available via telehealth.

What to Look For:

• App quality and insights
• Sensor comfort and accuracy
• Community/support access
• Integration with other health apps
• Coaching availability (if desired)

Recommendation:

Start with Levels or Veri for the best balance of cost, app quality, and educational value. The app insights are worth more than the hardware alone.

Compare All Options:

See OptimizeBiomarkers CGM Comparison Grid for detailed head-to-head comparisons of Levels, Nutrisense, Signos, Abbott Lingo, and more.

CGM Service Comparison:

CGM Hardware Options:

• Dexcom G7: ~$75-100/sensor (10 days)
• Freestyle Libre 3: ~$35-75/sensor (14 days)
• Stelo (Dexcom): OTC option, ~$99/month

Cost-Effective Approach:

1. Use a service like Levels for first 1-2 months (education phase)
2. Switch to direct sensor purchase for periodic check-ins
3. Total first-year cost: ~$400-800

Insurance/HSA:

• Not typically covered for non-diabetics
• HSA/FSA funds usually eligible
• Some services offer payment plans

Value Assessment:

CGM provides unique personalized data unavailable any other way. For metabolic optimization, the 1-2 month investment often yields insights that inform years of better decisions.

Notable Advocates:

• Dr. Casey Means - Co-founder of Levels, metabolic health advocate
• Ben Greenfield - Uses CGM for performance optimization
• Jessie Inchauspe (Glucose Goddess) - Popularized "glucose hacks"
• Dr. Robert Lustig - Metabolic health researcher

Scientific Leaders:

• Dr. Michael Snyder (Stanford) - Led glucotype research showing individual variability
• Research showing 24% of "healthy" individuals have prediabetic patterns

The Levels Team:

Founded by Dr. Casey Means and Josh Clemente, Levels has been instrumental in bringing CGM to the wellness market and funding metabolic health research.

Why CGM Became Popular:

• Tech industry adoption (Silicon Valley biohackers)
• Glucose Goddess (Jessie Inchauspe) social media
• COVID-era health optimization interest
• Levels marketing and education

What Users Report:

• "Finally understood why I crash after certain meals"
• "Discovered rice spikes me way more than bread"
• "Walking after meals is a game changer"
• "Sleep quality affects my glucose more than food"
• "Worth every penny for the education alone"

Common Discoveries:

1. Personal food triggers (often surprising)
2. Exercise timing matters more than expected
3. Sleep is the biggest glucose lever
4. Stress spikes are real
5. Food order affects response

Criticisms:

• "Expensive for temporary use"
• "Can create anxiety around eating"
• "Overkill for healthy people"
• "Insurance doesn't cover it"

Valid concerns - CGM is best as an educational tool, not permanent monitoring for healthy individuals.

Glucose Optimization Stack:

• CGM (monitoring)
• Time-restricted eating (meal timing)
• Walking 10k steps (post-meal walks)
• Zone 2 cardio (metabolic flexibility)
• Sleep environment (glucose control)

Metabolic Health Stack:

• CGM (data)
• Apple cider vinegar (glucose blunting)
• MCT oil (alternative fuel)
• Time-restricted eating
• 30-30-30 rule (protein-first approach)

Performance Stack:

• CGM (fueling optimization)
• Exogenous ketones (dual fuel)
• Zone 2 cardio (fat adaptation)
• Caffeine (timing with glucose)

Compare CGM Services:

• OptimizeBiomarkers CGM Comparison - Head-to-head comparisons of Levels, Nutrisense, Signos, Abbott Lingo, and more

Related Tracking Interventions:

• HRV training - Nervous system tracking
• CGM - Metabolic tracking
• Sleep tracking (Oura, Whoop) - Recovery tracking