Metabolic Adaptations to High-fat Diet

Adaptations in Postprandial Metabolic Flexibility Following a Three-day, High-fat Diet

The purpose of this study is to understand how the body's response after a meal is influenced by insulin and sugar in the blood. The primary question this study seeks to address is what is the effect of reduced insulin sensitivity on postprandial metabolic flexibility to an oral glucose tolerance test. We will recruit 50 adults (ages 20-45; 50% female) who are otherwise healthy (no known clinical diagnosis) into our non-randomized crossover trial to determine the effect of changes in insulin sensitivity on metabolic response to feeding. Insulin sensitivity will be decreased using a three-day high-fat diet (HFD) with extra calories. Whole-body metabolism will be measured during a standard 75-gram oral glucose tolerance test (OGTT). Metabolic response to feeding (e.g. OGTT) will be compared before and after the HFD and compared with the control diet to understand the effect of decreased insulin sensitivity on the metabolic response to feeding. The role of biological sex as a moderator of the effect of increased insulin resistance on postprandial metabolic flexibility will also be investigated

Inclusion Criteria:

• Males or Females between the ages of 20 and 45 years
• Body mass index (BMI) of 18.5-29.9 kg/m2
• Low risk for medical complications as determined by physical activity readiness questionnaire (PARQ).
• Low risk for food insecurity via the Hunger Vital Sign screener

Exclusion Criteria:

• Currently taking any antioxidant supplementation, prescription non-steroidal anti- inflammatory drugs, antibiotics, steroids, probiotics, medications for management of cholesterol, diabetes, body weight/obesity, or are undergoing transgender hormone therapy.
• Currently pregnant (verified by urine pregnancy test)
• Any history of disordered eating (i.e., anorexia nervosa, bulimia nervosa, binge eating disorder, etc.) or high risk for disordered eating via validated questionnaire (SCOFF)
• Any history of gastrointestinal diseases (i.e., gastroesophageal reflux disease, irritable bowel syndrome, Celiac disease, Crohn's disease, or lactose intolerance)
• Allergies to wheat or gluten, milk, soy, tree nuts (e.g., almonds, walnuts, pecans), or peanuts.
• Followed a ketogenic diet within the last three months
• Instructed by a medical provided to avoid a high-fat diet due to cardiovascular disease risk.
• Cardiorespiratory fitness (VO2max) greater than the 90th percentile for age and sex