What the Research Says
What the Blood Glucose Research Actually Shows
CGM research has transformed our understanding of individual glycaemic response. The evidence on glucose variability, food responses, and metabolic health is more nuanced than fasting glucose levels alone.
Beyond Fasting Glucose
Blood glucose research has been transformed by continuous glucose monitors (CGMs), which reveal post-meal patterns that fasting measurements miss. The key insight: two people eating identical meals can have dramatically different glucose responses, making individualised dietary guidance more important than population averages.
What Replicates Strongly
Post-meal glucose spikes are highly individual and often unpredictable from food GI alone. The Weizmann Institute's landmark CGM study (Zeevi et al., 2015, n=800) found that glycaemic response to identical foods varied up to 3-fold between individuals, and that the same individual responded consistently to the same food across days. Gut microbiome composition, meal timing, sleep, exercise, and stress all modulate the response — population-level GI tables are a poor predictor of individual response.
Post-meal glucose variability (not just average glucose) predicts metabolic outcomes. Research on glycaemic variability finds that high-amplitude swings — regardless of whether average glucose is normal — are associated with increased oxidative stress, inflammation, and risk markers for diabetes and cardiovascular disease. Time-in-range (70–140 mg/dL) is now considered more clinically important than HbA1c alone.
Walking after meals substantially reduces post-meal glucose peaks. RCTs consistently show that a 10–15 minute walk within 30 minutes of eating reduces post-meal glucose by 15–30% relative to sitting. The mechanism: muscle contraction activates GLUT4 transporters independently of insulin, increasing glucose uptake. Even low-intensity movement is effective; high-intensity exercise actually increases glucose acutely.
Meal composition order affects glucose response significantly. Multiple RCTs show that eating fibre and protein before carbohydrates in a meal reduces post-meal glucose peaks by 25–40% compared to eating carbohydrates first — even with identical total food. This is one of the most practical and cost-free glycaemic interventions identified by CGM research.
Poor sleep directly impairs insulin sensitivity. Spiegel, Tasali, and colleagues demonstrated that restricting sleep to 4–5 hours for one week reduced insulin sensitivity by 25%, producing glucose profiles characteristic of pre-diabetes in healthy young adults. Sleep is arguably the most powerful non-pharmacological tool for maintaining insulin sensitivity.
What the Research Can't Tell You
Individual glycaemic responses to specific foods — and the interventions that most effectively blunt them — are highly personal. Short-term CGM use (2–4 weeks) provides actionable data on your specific food responses, exercise timing effects, and sleep-glucose relationships that general dietary guidelines cannot. Many people discover that specific foods they assumed were "healthy" are significant glucose disruptors for them personally.