Diurnal Glycemic Redistribution in Obesity Despite Matched Mean Glucose

Background and Aims: Mean glucose and HbA1c reflect average glycemic exposure but do not capture its 24-hour distribution. When average glycemia is comparable, whether obesity is associated with a distinct temporal glucose pattern remains unclear. We compared continuous glucose monitoring (CGM) profiles in lean adults and adults with obesity matched for mean glucose. Methods: In a cross-sectional AI-READI analysis, lean adults (BMI 18.5 to <25 kg/m2) were matched one-to-one to adults with obesity (BMI >=30 kg/m2) by recruitment center and clinical group, with calipers for age, mean glucose and glucose standard deviation. CGM profiles were compared by clock time and relative to wearable-defined sleep onset. Sensitivity analyses tightened mean-glucose calipers from 10 to 2 mg/dL. Results: Among 261 matched pairs, mean glucose (lean versus obesity: 122.34 versus 122.82 mg/dL) and HbA1c (5.73% versus 5.78%) were comparable. Obesity was associated with higher nighttime glucose (00:00-06:00; +6.18 mg/dL) and lower afternoon glucose (12:00-18:00; -5.11 mg/dL; both adjusted P<0.001). Sleep-aligned analyses supported the nocturnal pattern, including among healthy participants and those with prediabetes. These differences persisted with a 2 mg/dL mean-glucose caliper (nighttime +3.86 mg/dL; afternoon -4.27 mg/dL; both adjusted P<0.001). Conclusion: Despite comparable mean glucose and HbA1c, obesity is associated with diurnal glycemic redistribution, characterized by higher nocturnal and lower daytime glucose. These findings support examining glucose timing alongside conventional measures of average glycemia.