Based on your blood results, you will be assigned to one of four study groups: participants with normal blood sugar levels (NG; control group); higher weight participants with normal blood sugar levels; higher weight participants who have pre-diabetes; higher weight participants who have type two diabetes. Participants of all four groups will consume a typical North American/Canadian diet for 4 weeks.
Figure 1: Summary of timeline and participant activities at each stage of the study
Visit 1 and 2 (Baseline visits)
Estimated time is 45-60 minutes on each visit day. Fasted blood measurements will be done on two consecutive days (by a trained phlebotomist – someone who is specially trained in taking blood). Blood sugar, lipid panel (cholesterol), C -reactive protein (CRP), Insulin, HbA1c, CBC (complete blood count) and differential, and immune levels will be measured in these blood samples. Depending on the time from screening to baseline we might also need to measure your weight, waist size and blood pressure. To get a good snapshot of what you usually eat, we will also give you instructions on how to fill out a food frequency questionnaire (from home). Lastly, you will need to fill out a physical activity and background questionnaire and collect a stool sample (if you are part of the stool sub-study) before study start.
4-week food consumption and food pick ups (Intervention)
You will eat a typical North American diet for 4 weeks to maintain your body weight. You will need to pick up your home cooked meals around three times a week at the HNRU, where we will also measure your weight (which will take about 10 minutes). You will take your weekend meals home on Fridays. You will need to bring all your food home and refrigerate it as soon as possible (maximum 1-hour window). The Study Coordinator will give you instructions on beverages other than water, outside of the study, that you can drink.
One time during the 4 weeks you will have your body fat analyzed using Dual Energy X-ray Absorptiometry (DXA). The purpose of the DXA scan is to assess body composition by quantifying bone, muscle and fat mass. This is a painless, non-invasive test. You will have to put on a hospital gown and lay on an x-ray bed. The scan takes 5 minutes. No special preparation is necessary. Women who participate in the study will have to complete a pregnancy test prior to the test to confirm you are not pregnant.
Visit 4 and 5 (Post-study)
Estimated visit time: for visit post-study visit Day 1, visit time is about 60 minutes and on Day 2, it is 3.5 to 4 hours. In post-study visit Day 1, you will have fasted blood taken (to look at lipid panel (cholesterol), blood sugar, CRP, Insulin, HbA1c and CBCD and the immune system). In post- study visit (Day 1), we will also need to measure your weight, blood pressure and waist/hip circumference.
In visit on Day 2, we will do an oral glucose tolerance test to measure blood sugar levels, which involves taking blood every 30 minutes for 3.5-4 hours after inserting an IV by a trained phlebotomist, after you drink a sugary beverage. Lastly, you will need to collect a stool sample and bring it back to us to us at either of your final visits.