Postprandial Glycemia and Satiety of Meals With Potatoes, With and Without Protein

The proposed study aims to simulate a meal eaten at home, where meals will provide a fixed amount of protein from beef or vegetarian substitute "meat" balls with ad libitum access to one of mashed potatoes, full-fat fries, or pasta. Postprandial glycemia (PPG), insulin, active ghrelin, satiety, amino acid response and food intake (FI) at the meal and again 3h later (after an ad libitum pizza meal) will be measured. In addition, post-meal PPG and satiety will be measured for one hour after the second meal.

A total of 30 participants (15 males, 15 females) will be recruited in this study at the University of Toronto. Each participant will attend 6 study sessions where they will consume meals consisting of a fixed amount of beef or vegetarian substitute "meat" balls providing 25 g protein with ad libitum access to one of mashed potatoes, fried French fries, or pasta. Questionnaires will be filled out to assess their recent food intake, physical activity, sleep quality, stress level, appetite, physical comfort, and energy/fatigue level, as well as palatability of the food.

Blood samples will be collected at fasting and at various time points over a 3 hour period after eating the meals to measure blood glucose, insulin, active ghrelin and amino acid concentrations. After 3 hours, participants will receive an ad libitum pizza meal to assess their food intake compensation. Post-meal PPG and satiety will be measured for one hour after the pizza meal.

Study hypothesis:

1. Consumption of potatoes in their most usual forms (mashed or deep fried), when compared with pasta in either meat or vegetarian based meals result in lower FI at the meal and lower PPG and insulin.
2. Compensation for the reduced FI in the mashed potato meal does not occur at a pizza meal 3h later.
3. Lower PPG and insulin post-test meal and second meal will be found.
4. The amino acid profile of different meals will be reflected in post-prandial plasma levels and the amino acid response to vegetarian based meals with potatoes will be more balanced compared to the vegetarian based meals with pasta.

Primary objective:

To investigate the effects of potato consumption served with either meat or vegetarian substitute "meat" on meal-time FI and PPG, insulin, satiety and FI compensation at a later meal in healthy and normal weight adults. FI and PPG are primary outcomes and satiety, insulin, active ghrelin, amino acid response and FI compensation are secondary outcomes.

Specific Objectives:

Objective 1: To simulate at home-style meals and determine their effects on FI, satiety, PPG, and insulin, over three hours. Meals will be served with a fixed amount of beef or vegetarian substitute "meat" balls providing 25 g protein with ad libitum access to one of mashed potatoes, fried French fries, or pasta.

Objective 2: To determine the effect of at home-style meals with beef or a vegetarian substitute with mashed potatoes on FI compensation at an ad libitum pizza meal 3h later. Post-meal PPG and satiety will be measured for one hour.

Objective 3: To compare the amino acid response for 3 h after the meat and vegetarian based meals served with mashed potatoes, French fries, or pasta.

Eligibility Criteria:
Inclusion Criteria:

* \> 18 and \< 45 years of age
* BMI \> 18.5 and \< 24.9 kg/m2
* Willing to maintain habitual diet, physical activity pattern, and body weight throughout the study.
* Willing to maintain current dietary supplement use throughout the study. On test days, subject agrees not to take any dietary supplements until dismissal from the Nutrition Intervention Center. Failure to comply will result in a rescheduled test visit.
* Willing to abstain from alcohol consumption for 24h prior to all test visits.
* Willing to refrain from marijuana/ edibles use for the duration of the study (approximately 6 weeks).
* Willing to avoid vigorous physical activity for 24h prior to all test visits.
* Understanding the study procedure and willing to provide informed consent to participate in the study and authorization to release relevant protected health information to the study investigator.

Exclusion Criteria:

* Smoking
* Thyroid problems
* Previous history of cardiovascular disease, diabetes, liver or kidney disease, inflammatory bowel disease, celiac disease, short bowel syndrome, a malabsorptive syndrome, pancreatitis, gallbladder or biliary disease.
* Presence of a gastrointestinal disorder or surgeries within the past year.
* Known to be pregnant or lactating.
* Unwillingness or inability to comply with the experimental procedures and to follow our safety guidelines.
* Known intolerances, sensitivity or allergy to any ingredients in the study products.
* Extreme dietary habits (i.e Atkins diet, very high protein diets, etc.) or restrained eaters, identified by a score of ≥ 11 on the Eating Habits Questionnaire
* Uncontrolled hypertension (systolic blood pressure \> 140 mm Hg or diastolic blood pressure \> 90 mm Hg) as defined by the average blood pressure measured at screening.
* Weight gain or loss of at least 10lbs in previous three months.
* Excessive alcohol intake (more than 2 drinks per day or more than 9 drinks per week).
* Consuming prescription or non-prescription drug, herbal or nutritional supplements known to affect blood glucose or that could affect the outcome of the study as per investigator's judgment.