The PREVIEW New Zealand study: Prevention of Type 2 Diabetes through Lifestyle Intervention in a Cohort of Overweight Adults with Pre-Diabetes

Abstract

The prevalence of obesity worldwide has increased to a pandemic with more than 1.9 billion people classified as overweight and 600 million classified as obese. Obesity is the cause of long-term chronic disease; affecting social and economic costs worldwide. New Zealand is no exception being 3rd in the OECD for obesity, behind USA and Mexico. More than two-thirds of New Zealanders are overweight and from which 50% are classified as obese. Obesity contributes directly to the cause of T2D; hence, the increasing obesity leads to the increase in the incidence of T2D. This thesis investigates whether dietary intervention, which is aimed at short-term rapid weight loss and then longer-term weight loss maintenance, can be successful for the prevention of T2D in a cohort of overweight, pre-diabetic adults in Auckland, New Zealand. In particular, investigating whether a higher protein, lower glycaemic index (GI) diet is more successful than a higher carbohydrate (CHO), moderate GI diet for weight loss maintenance, and in turn better T2D related metabolic outcomes. This research was part of the larger international PREVIEW (PREVention of diabetes In Europe and Worldwide) intervention. The aim of this PREVIEW:NZ study thesis investigates the benefits of short term 8-week acute LED-induced weight loss and longer term (2 year) lifestyle-induced weight change on metabolic parameters associated with risk of T2D in Caucasian, Maori/Pacific and Other ethnicity subgroups. The aim of the GI substudy was to analyse the GI of kumara to be able to make diet recommendations in the lifestyle intervention weight maintenance phase. The primary objectives for PREVIEW:NZ were to investigate changes to body weight, body composition and metabolic markers during an 8-week low energy diet (LED) rapid weight loss phase and then a 2-year lifestyle weight maintenance phase where the diet recommendations were for lower-fat, higher protein, lower GI versus lower-fat, higher CHO, moderate GI; and also to investigate gender and ethnicity differences. A secondary objective was to investigate the GI of sweet potato/kumara, a high CHO staple commonly consumed in New Zealand and an important food in PREVIEW:NZ. The main hypothesis was that, an ad libitum novel low fat, higher protein, lower GI diet would result in better weight loss maintenance and T2D-related metabolic markers when compared to a traditional low fat, higher CHO, moderate GI diet that adheres to current recommendations for T2D prevention.