(P22-026-23) Effect of Dairy Fat Consumption on Insulin Sensitivity in People With Overweight or Obesity With Prediabetes: A 12-Week Randomized Controlled Trial Protocol

Objectives: Type 2 diabetes (T2D) is a major public health issue worldwide. Recent epidemiological evidence shows that higher intake of total dairy foods is associated with lower T2D risk, especially when dairy-specific fatty acids are used as biomarkers of dairy fat intake. Evidence from randomized controlled trials (RCT) is inconclusive, possibly due to the use of surrogates of insulin sensitivity (IS). Our primary objective is to determine the effect of dairy fat intake on IS in individuals with prediabetes. We also assess changes in glycemic measures, body composition, and cardiovascular markers as secondary outcomes.

Methods: We aim to recruit 75 males and females aged 30-65y with overweight or obesity with prediabetes. Eligible individuals enter a 2-week run-in period with an intake of 1 serving/d of low-fat dairy foods. Adherent participants (n=60) are randomized (1:1:1 stratified by sex) to 1 of the 3 groups for the 12-week intervention: 1) ≤1 dairy serving/d; 2) 2-3 servings/d of skim milk, non-fat yogurt and low-fat cheese; 3) 2-3 servings/d of regular-fat milk, yogurt and cheese. Participants are instructed to incorporate study foods while maintaining their usual body weight (±5%) and lifestyle. Adherence is assessed by dairy intake logs, monthly 3-day image-based food diaries, and serum proportion of 15:0, 17:0, and t16:1n7 fatty acids as dairy fat biomarkers. Physical activity is assessed with a questionnaire and accelerometry.

For the primary outcome, we assess changes in IS with the gold-standard hyperinsulinemic-euglycemic clamp before and after the intervention. Briefly, insulin is infused intravenously at 40 mU/m²/min for 2h; 20% glucose is infused at variable rates to maintain serum glucose levels at 5.5 mmol/L, determined by 5-min measurements. Moreover, we measure glucose tolerance by the 75g oral glucose tolerance test, body composition by dual-energy X-ray absorptiometry, and lipid profile by clinical chemistry. The effects on measured outcomes will be assessed using linear mixed models in intent-to-treat and per-protocol analyses.

Results: The trial is registered on ClinicalTrial.gov (NCT05421390). Recruitment and data collection are ongoing.

Conclusions: Our findings will help resolve current uncertainties about the role of dairy in T2D at an early stage and this could impact dietary recommendations.

Funding Sources: Dairy Farmers of Canada