Why the same food affects different people very differently.
What the evidence says
- Blood sugar responses to identical foods show ”high interpersonal variability”[1]
- Study of 800 people measuring responses to 46,898 meals found high variability[1]
- Individual responses are highly reproducible within the same person (R = 0.71-0.77 for standardized meal replicates), while responses to the same meal show ”high interpersonal variability”[1]
- Factors affecting individual response include: blood parameters, dietary habits, anthropometrics, physical activity, gut microbiota[1]
- The high variability is ”suggesting that universal dietary recommendations may have limited utility”, and the carbohydrate-counting model predicts postprandial glycemic response only modestly (R = 0.38; calories alone, R = 0.33)[1]
- The paper finds ”wide variations in postprandial responses between people, even identical twins”. *The authors’ own conclusion: variation is ”attributable in large part to modifiable factors”***[2]
- For postprandial glycemia, meal macronutrients explain more of the variance than the gut microbiome (15.4% against 6.0%, the abstract’s comparison); heritability is 30% but SNP-based genetics only ~9%[2]
- Same meal consumed at lunch produced 2-fold higher glycemic response than at breakfast (mean glucose iAUC 14,254 vs 7,216), the lunch taken 4 hours after the challenge breakfast[2]
- Machine learning algorithm integrating personal and microbiome features predicts individual glycemic response with R = 0.68-0.77, validated on independent cohorts[1],[2]