The primary objective is to investigate the impact of milk, fermented milk, and soy beverages, incorporated in a diet reflecting adherence to Canadian food guide recommendations on food choices on gut microbiota in middle-aged adults (45-65 years) with abdominal obesity and slightly deteriorated lipids and/or glucose profile. The study aims to discern whether the integration of soy beverages (control), milk, and fermented milk within the CFG diet contributes to distinct gut outcomes and alterations in gut health. We hypothesized that milk and fermented milk will further promote beneficial changes in gut health parameters including gut microbiota composition, trans-epithelial permeability, and inflammation, relative to soy beverages.

Single-blinded crossover RCT to test the impact of integrating dairy (i.e., milk and fermented milk) into the Canadian Food Guide (CFG) diet on gut health, in fully controlled dietary settings. The trial will include mid-age women and men with abdominal obesity and slightly deteriorated metabolic profile (n=20). The trial will feature 3 controlled-feeding phases (14 days), allocated in a random order and separated by free-uncontrolled feeding washout periods (14-28 days). Each dietary intervention phase will be initiated by a Run-in full-feeding period (4 days), to standardize participants' dietary intakes, and immediately followed by one of the 3 dietary interventions (9 days) reflecting adherence to the CFG recommendation (9 days, CFG-Diet) incorporating either soy beverages (Control), milk, or non-effervescent fermented milk.

This approach was shown to be highly informative in deciphering the interaction between diet and the gut microbiota in previous work. It will be able to assess how integrating dairy (i.e., milk and fermented milk) into the Canadian Food Guide (CFG) diet promptly modulates gut health parameters (i.e. gut microbiota composition, inflammatory states, and gut permeability) in the context of obesity and metabolic complications, relative to a plant-based alternative. The fully controlled dietary setting of this study design will provide precise intakes of foods and bioactive nutrients, which will enable us to comprehensively assess the impact of dairies on gut health.

The trial will include 10 women and 10 men with abdominal obesity and slightly deteriorated metabolic profile.

Diet sequence allocation will be randomized with a sex-specific stratification. The study will be single-blinded, such as participants will not be informed of the precise nature of the diet sequence.

TRIAL INTERVENTION PHASES (3 X 14 DAYS)

During each intervention phases, all meals and foods will be provided to ensure optimal diet control. Each intervention phases will follow this sequence:

• Day 0: Initiation of the run-in full-feeding period (4 days) to standardize participants' dietary intakes.
• Day 4: Baseline sampling and data collection.
• Day 4: Initiation of the CFG dietary intervention (10 days) incorporating either soy beverages (Control), milk, or non-effervescent fermented milk.
• Day 6: Post-intervention (+2 days) sampling and data collection.
• Day 13: Post-intervention (+9 days) sampling and data collection. End of the intervention phases.

Inclusion Criteria:

• IMC < 45
• Waist circumference > 80 cm (Women) or 94 cm (men)

Exclusion Criteria:

• History of diabetes (types 1 and 2), CVD, enteropathy, immune diseases or bariatric surgery
• Cancer (diagnostic and/or treatment) during the last 5 years
• Antibiotic consumption during the last 3 months
• Active smoking or cannabis consumption
• Lactose intolerance or allergy, any allergies to foods given in the intervention phases
• Irregular defecation patterns
• Pregnancy/lactation
• Inability to speak French

All IPD that underlie results in a publication