Glycaemic, appetite and circadian benefits of a dairy-enriched diet with high-protein breakfast and early daytime-restricted carbohydrate intake in type 2 diabetes: a randomised crossover trial

AIMS/HYPOTHESIS: The circadian timing of food intake and the composition of dietary protein sources may jointly influence metabolic regulation. Our aim was to examine the effects of a dairy-enriched vs non-dairy isoenergetic diet with structured meal timing on circadian clock gene expression, glycaemic management and appetite regulation in individuals with type 2 diabetes. METHODS: ≥48 mmol/mol (6.5%), treated either with stable doses (≥3 months) of oral glucose-lowering agents or managed by diet, followed two 4 week dietary phases, one including dairy-based protein sources (YesMilk) and one excluding them (NoMilk), with a 3-4 week washout. Participants were randomly assigned to one of two intervention sequences using simple randomisation (coin flip), either starting with the YesMilk diet followed by the NoMilk diet, or vice versa. Due to the open-label design, allocation was not concealed from investigators or participants. The study was powered for the primary outcome of circadian clock gene expression in peripheral blood mononuclear cells. Secondary outcomes included glycaemic indices derived from continuous glucose monitoring (CGM) and appetite scores. The study was conducted via the Diabetes Unit at Wolfson Medical Center, Israel. RESULTS: Twenty-nine individuals were screened; 25 met eligibility criteria and were randomised to YesMilk or NoMilk dietary interventions in a crossover design. Thirteen participants began with the YesMilk dairy diet, all of whom completed both phases. Of the 12 who began with the NoMilk diet, six completed the study. Nineteen participants completed both intervention phases. Compared with the NoMilk phase, the YesMilk diet upregulated BMAL1 (+1.8-fold, p=0.0003), REV-ERBα (also known as NRD1D1) (+2.2-fold, p