Designing strategies to improve and measure adherence to dietary weight loss interventions in research and real world settings

Abstract

Background: The optimal dietary approach to weight loss is a hotly debated topic among health professionals and the lay public alike. An emerging body of evidence suggests that a higher level of adherence to a diet, regardless of the type of diet, is an important factor in weight loss success over the short and long term. The overall aim of this thesis was to examine how dietary interventions can be designed to improve and measure adherence and thereby increase the success of dietary weight loss interventions. Methods: Four studies were conducted to achieve this aim. Study 1 (Chapter 2) is a systematic review and meta-analysis of appetite responses to two types of ketogenic diets (very low energy diets, VLEDs; and ketogenic low carbohydrate diets, KLCDs). Study 2 (Chapter 3) is a modelling study that presents the design process and underlying rationale of the dietary intervention of a study comparing fast versus slow weight loss. Study 3 (Chapter 4) compares the nutritional content, nutritional adequacy and cost of all VLED products in Australia. Study 4 (Chapter 5) is a validation study of a new method that was developed to improve the accuracy of portion size estimation and in so doing, measures of adherence. Results and discussion: Study 1 found that VLEDs and KLCDs are indeed associated with a suppression of appetite and that ketosis is a plausible mechanism underlying the effect. Study 2 demonstrated the feasibility of designing a food-based, moderately energy-restricted diet that can be individualized to a person’s dietary preferences, while still aligning with dietary guidelines and containing adequate protein for women of various sizes. Study 3 provides practical clinical guidance by demonstrating how commercially available VLEDs can be optimised in protein, which could improve adherence via increased appetite control. Study 4 found that the new method of estimating portion sizes could improve the accuracy of portion size estimation methods which may improve adherence measures. Conclusions: There are several key targets that have the potential to improve and measure adherence to dietary weight loss interventions and thereby weight loss success. By examining the design of strategies that are practical, affordable and feasible, the findings of this thesis have direct implications for clinicians tackling the obesity epidemic in research and real world settings.