Postprandial responses to food are highly dependent on the macronutrient composition of the diet. We investigated the acute effects of transition from the recommended moderately high
carbohydrate (HC) diet towards a
carbohydrate-reduced high-
protein (CRHP) diet on postprandial glycemia, insulinemia,
lipemia, and appetite-regulating
hormones in non-diabetic adults. Fourteen subjects, including five males (Mean ± SD: age 62 ± 6.5; BMI 32 ± 7.6 kg/m²;
hemoglobin A1c (HbA1c) 40 ± 3.0 mmol/mol; HOMA2-IR 2.1 ± 0.9) were included in this randomized, cross-over study. Iso-caloric diets were consumed for two consecutive days with a median wash-out period of 21 days (range 2⁻8 weeks) between diets (macronutrient energy composition: CRHP/HC; 31%/54%
carbohydrate, 29%/16%
protein, 40%/30% fat). Postprandial
glucose, insulin secretion rate (ISR),
triglycerides (TGs), non-
esterified fatty acids (NEFAs), and satiety ratings were assessed after ingestion of breakfast (Br) and lunch (Lu), and gut
hormones and
glucagon were assessed after ingestion of Br. Compared with the HC diet, the CRHP diet reduced peak
glucose concentrations (Br 11%, p = 0.024; Lu 11%, p < 0.001),
glucose excursions (Br 80%, p = 0.20; Lu 85%, p < 0.001), and ISR (Br 31%; Lu 64%, both p < 0.001) whereas CRHP, as compared with HC, increased
glucagon-like peptide-1 (Br 27%, p = 0.015) and
glucagon values (Br 249%, p < 0.001).
NEFA and TG levels increased in the CRHP diet as compared with the HC diet after Br, but no difference was found after Lu (
NEFA Br 22%, p < 0.01; TG Br 42%, p = 0.012). Beta-cell
glucose sensitivity, insulin clearance,
cholecystokinin values, and subjective satiety ratings were unaffected. It is possible to achieve a reduction in postprandial glycemia and
insulin without a deleterious effect on beta-cell
glucose sensitivity by substituting part of
dietary carbohydrate with iso-caloric
protein and fat in subjects without
type 2 diabetes mellitus (T2DM). The metabolic effects are more pronounced after the second meal.