What will happen in the study?

Based on your screening results, you will be assigned to one of four study groups: subjects with normal blood sugar levels (NG; control group); subjects with obesity and with normal blood sugar levels; subjects with obesity who have pre-diabetes; subjects with obesity who have type two diabetes. Participants will then consume a typical North American/Canadian diet for 4 weeks.

Figure  1: Summary of timeline and participant activities at each stage of the study

*FFQ = food frequency questionnaire
**DXA = Dual Energy X-ray Absorptiometry measurement
***Part of stool sub-study (which requires separate consent form)

Visit 1 and 2 (Pre-study)

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, cholesterol and immune levels will be measured in these blood samples. In each of these two days, we will also need to measure your weight, height, 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, we will need you 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.

Visit 3 (Intervention)

During these 4 weeks, you will eat a typical North American diet to maintain your body weight. You will need to pick up your home cooked meals daily 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 are most welcome to stay and eat in the kitchen of the HNRU at lunch time or you can take your food and go. There are also weekly lunch and learn nutrition presentations available for you. The Study Coordinator will give you instructions on beverages other than water, outside of the study, that you can drink.

Visit 4 and 5 (Post-study)

Estimated visit time: for visit 4, visit time is about 60 minutes and on visit 5, it is 3.5 to 4 hours. In visit 4, you will have fasted blood taken (to look at cholesterol and the immune system) and have your body fat analyzed using Dual Energy X-ray Absorptiometry (DXA). In visit 4 we will also need to measure your weight, blood pressure and waist size. In visit 5, we will do an oral glucose tolerance test to measure blood sugar levels, which involves taking blood every 30 minutes for 3 hours 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 at visit 4 or 5.