Lifestyle intervention programmes are efficacious in the management of obesity but often report poor attendance and adherence rates that hinder treatment effectiveness and health outcomes. The aim of this systematic review is to identify (i) barriers to behaviour change and (ii) predictors of adherence to lifestyle intervention programmes in adults with obesity. Studies were identified by systematically reviewing the literature within Medline, PsycINFO, CINAHL, SPORTDiscus and Web of Science from inception to August 2016. Barriers to behaviour change include poor motivation; environmental, societal and social pressures; lack of time; health and physical limitations; negative thoughts/moods; socioeconomic constraints; gaps in knowledge/awareness; and lack of enjoyment of exercise. The most prominent predictors of adherence include early weight loss success, lower baseline body mass index (BMI), better baseline mood, being male and older age. The findings within this review provide novel insight to clinicians working in obesity and have important implications for lifestyle intervention programme design. Barriers to behaviour change need to be addressed early in treatment, with lifestyle intervention individualized accordingly. Predictors of adherence should also be taken into careful consideration, with negative moods and unrealistic weight loss expectations discussed at the outset. If adherence is improved, treatment effectiveness, health outcomes and the ultimate burden of chronic diseases could also be improved.