"In the latter half of the 20th Century increases in the availability of inexpensive, energy-dense foods combined with an estimated 60-70% reduction in daily energy expenditure, created an “obesogenic” environment. The epidemic of obesity that has emerged has been associated with the Metabolic Syndrome (MetS) which is a cluster of risk factors that are precursors to chronic diseases including cardiovascular disease (CVD), type II diabetes (T2D), stroke, and dementia. These chronic diseases are having a significant social and economic impact worldwide with their related morbidity and mortality. Epidemiological and interventional studies have shown that lifestyle interventions based on a low-fat, plant-based diet are effective for the management of MetS and associated chronic diseases. To date, the research has focused on lifestyle interventions delivered by professional facilitators, mostly in clinical settings. The primary aim of this dissertation was to examine the effectiveness of a lifestyle intervention known as the Coronary Health Improvement Program (CHIP), when delivered by volunteer facilitators to free-living participants in their community. The secondary aim of the dissertation was to examine the impact of selected participant factors including age, gender, religious affiliation, marital status, previous history, family history and body mass index on the participants’ responsiveness to the CHIP intervention. This study adopted a pre-test post-test design involving, a large cohort of 5070 individuals who participated in one of 178 community-based CHIP interventions delivered by volunteers between 2006 to 2009 in the United States and Canada. In 30 days, significant reductions (p < 0.001) were recorded in body mass index (3.2%), total cholesterol (11.0%), low-density lipoprotein cholesterol (13.0%), triglycerides (7.7%), fasting plasma glucose (6.1%) and systolic and diastolic blood pressure (4.9% and 5.3%, respectively). Stratification of the data revealed larger reductions in those participants who presented to the program with the greatest risk factor levels. Regardless of age, gender, marital status, religious affiliation, previous history, family history and body weight, participants in the CHIP intervention achieved significant improvements in the risk factors associated with MetS however these factors influenced the responsiveness of the participants to the program. In general, male participants achieved better results than the females, and males tended to achieve their best outcomes at a younger age than the female participants. Married participants achieved better outcomes than single, divorced or widowed participants. Seventh-day Adventist (SDA) participants had better risk profiles at baseline, however, the non-SDA participants achieved better outcomes during the intervention. Participants who had the highest body mass index (BMI) at baseline achieved the greatest changes in BMI, fasting plasma glucose and blood pressure, however, those participants with a BMI greater than 35 kg/m2 showed significantly less improvement in their lipid profile than those participants with a BMI between 25 and 35 kg/m2. It was concluded that significant reductions in the risk factors associated with MetS can be achieved in 30 days using the CHIP lifestyle intervention when delivered by volunteers to free-living participants in their local community. Significant reductions in risk factors associated with MetS can be achieved regardless of age, gender, marital status, religious affiliation or baseline biometrics. Utilising volunteers may therefore provide an effective and cost-efficient mode of delivering lifestyle interventions targeting MetS."