Age, Sex, BMI, Meal Timing, and Glycemic Response to Meal Glycemic Load.

Importance: Postprandial glycemic responses contribute to comorbidities and mortality risk, but the association between food and postprandial glucose responses in general population settings remains uncertain.

Objective: To investigate the association of dietary glycemic load (GL), meal timing, age, sex, body mass index (BMI), and glycated hemoglobin (HbA1c) concentration with postprandial glycemic response to mixed meals.

Design, setting, and participants: This cross-sectional study was conducted from August 21, 2012, to March 26, 2015, at a primary health care center in A Estrada, northwestern Spain. A population-based sample of adults aged 18 to 85 years without diabetes who were randomly selected from National Health System records agreed to participate. Data analysis was performed between April 20, 2023, and March 26, 2024.

Exposure: The main exposure was dietary GL. Additional exposures included age, sex, BMI, meal timing, and HbA1c concentration.

Main outcome and measures: Postprandial glucose response over 3 hours after breakfast, lunch, and dinner was assessed using continuous glucose monitoring (CGM) for 7 days, with dietary assessments. Multilevel regression models evaluated the association between GL and glucose dynamics, accounting for age, sex, BMI, meal timing, and HbA1c concentration.

Results: Of the 622 participants fitted with the CGM device, 514 (median age, 46 years [IQR, 36-58 years]; 64% females) met eligibility criteria and provided analyzable data. More than 1.3 million glucose measurements were analyzed across 2451 days. Dietary GL was associated with higher postprandial blood glucose levels, with maximum rises of up to 1.3 (95% CI, 0.8-1.8) mg/dL per 10 units of GL. Glucose responses were greater and more prolonged after lunches and dinners than after breakfasts, with peak values observed at 70 minutes after lunches and dinners and 50 minutes after breakfasts. Each 10-year increase in age was associated with an increase in postprandial glucose levels of 1.9 (95% CI, 0.6-3.3) mg/dL to 3.5 (95% CI, 2.2-4.8) mg/dL, while BMI was associated with glucose response after breakfast, with increases of up to 0.7 (95% CI, 0.4-1.1) mg/dL per BMI unit increase. Men had lower glucose levels than women during the late postprandial period after lunch and dinner, with differences of up to 4.6 (95% CI, 1.6-7.6) mg/dL. HbA1c concentrations and meal timing were also associated with postprandial glucose levels (eg, glucose levels increased up to 12.0 [95% CI, 6.5-17.5] mg/dL per 1% increase in HbA1c).

Conclusions and relevance: In this cross-sectional study of adults without diabetes, higher-GL meals were associated with sustained postprandial glucose elevations, especially after lunch and dinner. Age, sex, BMI, meal timing, and HbA1c concentration were also associated with glucose responses. These findings support the validity of dietary GL as an explanatory factor for glycemic response to mixed meals under typical everyday conditions when meal timing, age, and BMI are considered.