A feasibility study to investigate the effectiveness and safety of an intermittent fasting diet for weight reduction in adults with Type 2 Diabetes treated with insulin : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Human Nutrition at Massey University, Albany, New Zealand

Abstract

Background: Type 2 diabetes (T2DM) is the most common form of diabetes. Obesity is associated with both the development of T2DM and also the development of the complications of diabetes; increasing health care costs and morbidity and mortality. Weight loss and control of blood glucose levels should be managed with a tailored eating plan developed in negotiation between the person with diabetes and their health care team. It is essential that health care professionals are familiar with different strategies that achieve weight reduction, glycaemic and cardiovascular risk reduction goals. One emerging weight reduction strategy is fasting diets. There is currently a gap in the knowledge of whether fasting diets are an effective and safe weight reduction strategy for people with T2DM on insulin. Aim: To investigate the effectiveness and safety of an intermittent fasting diet (two day per week) as an alternative to standard dietary advice (portion control diet) for weight reduction in obese adults with insulin dependent T2DM attending a 12-week group based intervention at Waitemata District Health Board (DHB). Methods: Obese patients with T2DM treated with insulin who were attending Waitemata DHB Diabetes Service were recruited for this two arm open-label design intervention feasibility study. Both dietary strategies were implemented during a 12-week intervention at which participants received monthly dietitian-led group education and support. The intermittent fasting diet (IFD) intervention (n=8) investigated was a two day per week reduced energy intake (550-650kcal / 2300- 2700kJ per day) and five days’ usual intake making low fat choices. The portion control diet (PCD) was the comparison group (n=7) and focused on daily energy restriction through reduction in portion sizes and low fat food choices in line with current New Zealand dietary recommendations for management of T2DM. Results: Similar weight loss was achieved in both groups (IFD: 2.7 ± 3.0 kg, PCD: 1.7 ± 2.5 kg). This reduction was not significant between groups. There was a significant difference between groups in reduction in HbA1c. (P=0.003) (IFD: -11 mmol/mol, PCD: -3 mmol/mol). This decrease was significant in the IFD group only (P=0.018). Reported hypoglycaemic events were low in both groups (8 events in IFD; 21 events in PCD). Non-significant between group reductions in waist circumference (P=0.402), waist: height ratio (P=0.455), diastolic (P=0.189) and systolic blood pressure (P=0.443) were observed. Lipid profile remained stable in both groups. Conclusion: This feasibility study showed that an intermittent fasting diet can achieve similar weight loss to current standard practice dietary advice in people with T2DM. However, it is the significant reductions in HbA1c compared to a daily energy restriction diet over a three-month period seen in this study that warrant further investigation. With education from health care professionals and modification of insulin on pre-fasting and fasting day this diet may be followed safely and hypoglycaemia avoided or managed appropriately.