Secondary Outcomes (explanation)
1. Two dietary assessment tools will be used to characterize subjects’ diets. A Food Frequency Questionnaire (FFQ) and a Medicross paper food diary for diabetes patients.
First, at Visit 1, participants will complete a self-administered FFQ (Appendix C) asking about foods eaten in the past month. The instrument has been used in previous studies in South Africa and can also be used online (Webster, Murphy, Larmuth, Noakes and Smith, 2018). The FFQ was developed according to guidelines proposed by Cade, Thompson, Burley, & Warm (2002) by adapting the South African Medical Research Council’s (MRC) FFQ (Steyn & Senekal, 2004) to include food items frequently eaten by people following a low carbohydrate diet. It also includes standard portion sizes (to increase accuracy of macronutrient ratio estimation), and frequency options (necessary for an online questionnaire). The FFQ data will be used to assess the types of foods eaten and macronutrient ratios rather than absolute nutrient quantities. Macronutrient ratios will be determined from FFQ data by multiplying the frequency of food items eaten per month, by their respective assigned macronutrient contents. Macronutrient content will be derived from the FatSecret database and MRC’s SAFOODS database, because MRC’s SAFOODS database omits many low carbohydrate food choices. The FFQ will be re-administered (Visit 5) to assess the sustainability of healthy-eating habits formed during the intervention.
Second, participants will be asked to keep a food diary for four days during the beginning of the baseline and four days towards the end of the CGM intervention. The four days will include weekends and weekdays. We are interested in quality over quantity of data so we do not insist on daily entries. However, patients may enter the diary daily if they wish. Besides the common limitations of self-report measures (e.g. deception, guessing, non-compliance), there is a risk of missing data when asking individuals to enter their food intake since they could forget or become fatigued. Omissions in the food diary will be followed up on. We will also learn from compliance rates in entering data about the usefulness of such diaries as a measure of self-reported dietary intake. For the treatment groups, it will be interesting to correlate compliance behaviours such as number of food diary days completed and number of scans per day using Freestyle Libre CGM (engagement in self-monitoring). Qualitative comparisons will be discussed between temporal glucose patterns and reported dietary intake. Our analysis of participants’ food choices will be explorative.
2. Lipid panel will be measured at baseline and endline (blood test).
3-4. Body composition (including waist and hip circumference, weight, height) and blood pressure will be taken at baseline and regular checkups with study physician.
5-6. The participant will complete a self-administered baseline questionnaire to assess demographics (including income bracket and education), tobacco and alcohol consumption, physical activity, diabetes, cardiovascular disease and blood pressure history, risk and time preferences, math ability, subjective wellbeing, and diabetes distress. Our baseline questionnaire includes sections from validated questionnaires. Prevalence and severity of diabetes is strongly associated with socioeconomic and cultural factors, such as income, education, gender, ethnicity and culture. Subjective wellbeing and diabetes distress will be measured at baseline and endline.
Subjective wellbeing will be measured using a single standard item and scored on a scale of 1 to 10 where 1 means “very dissatisfied” and 10 means “very satisfied”: “How do you feel about your life as a whole right now?”. The wording of this standard measure of subjective wellbeing is sourced from the South African National Income Dynamics Study (NIDS). This measure may be affected by social distancing and economic hardship due to SARS-CoV2 restrictions, which will be recorded.
We will use the Diabetes Distress Scale (DDS) for adults with type 2 diabetes. The DDS is a 17-item self-report instrument. Each item is rated on a 6-point scale from (1) “not a problem” to (6) “a very significant problem”. The scale yields an overall distress score based on the average responses on the 1-6 scale for all 17 items. It can also be used to get a measure of emotional burden (average of 5 items), physician distress (average of 4 items), regimen distress (average of 5 items) and interpersonal distress (average of 3 items). Average score < 2.0 reflects little or no distress. Average score 2.0 – 2.9 reflects moderate distress and > 3.0 reflects high distress. A total or subscale score > 2.0 is considered clinically significant.