Associations of changes in reported and estimated protein and energy intake with changes in insulin resistance, glycated hemoglobin, and BMI during the PREVIEW lifestyle intervention study

Background: Observed associations of high-protein diets with changes in insulin resistance are inconclusive. Objectives: We aimed to assess associations of changes in both reported and estimated protein (P-Rep; P-Est) and energy intake (EIRep; EIEST) with changes in HOMA-IR, glycated hemoglobin (HbA1c), and BMI (in kg/m(2)), in 1822 decreasing to 833 adults (week 156) with overweight and prediabetes, during the 3-y PREVIEW (PREVention of diabetes through lifestyle intervention and population studies In Europe and around the World) study on weight-loss maintenance. Eating behavior and measurement errors (MEs) of dietary intake were assessed. Thus, observational post hoc analyses were applied. Methods: Associations of changes in EIEst, EIRep, P-Est, and P-Rep with changes in HOMA-1R, HbA1c, and BMI were determined by linear mixed-model analysis in 2 arms [high-protein-low-glycemicindex (GI) diet and moderate-protein-moderate-GI diet] of the PREVIEW study. EI Est was derived from energy requirement: total energy expenditure = basal metabolic rate x physical activity level; P-Est from urinary nitrogen, and urea. MEs were calculated as [EIEst - EIRep)/EIEst] x 100% and [(P-Rep- P-Est)/P-Est] x 100%. Eating behavior was determined using the Three Factor Eating Questionnaire, examining cognitive dietary restraint, disinhibition, and hunger. Results: Increases in P-Est and P-Rep and decreases in EIEst and EIRep were associated with decreases in BMI, but not independently with decreases in HOMA-IR. Increases in P-Est and P-Rep were associated with decreases in HbA1c. P-Rep and EIRep showed larger changes and stronger associations than P-Est and EIEst. Mean +/- SD MEs of EIRep and P-Rep were 38% +/- 9% and 14% +/- 4%, respectively: ME changes in EIRep and En% P-Rep were positively associated with changes in BMI and cognitive dietary restraint and inversely with disinhibition and hunger. Conclusions: During weight-loss maintenance in adults with prediabetes, increase in protein intake and decrease in energy intake were not associated with decrease in HOMA-IR beyond associations with decrease in BMI. Increases in P-Est and P-Rep were associated with decrease in HbA1c.