Background Integrating professional expertise in diet, exercise and behavioural support may provide more effective preventive health services but this needs testing. We describe the design and baseline results of a trial in the Illawarra region of New South Wales, Australia. Methods The HealthTrack study is a 12 month randomised controlled trial testing effects of a novel interdisciplinary lifestyle intervention versus usual care. The study recruited overweight and obese adults 25-54 years resident in the Illawarra. Primary outcomes were weight, and secondary outcomes were disease risk factors (lipids, glucose, blood pressure), and behaviour (diet, activity, and psychological factors). Protocols, recruitment and baseline characteristics are reported. Results Between May 2014 and April 2015, 377 participants were recruited and randomised. The median age (IQR) of the mostly female sample (74%) was 45 (37-51) years. The sample comprised obese (BMI 32 (29-35) kg/m2) well educated (79% post school qualifications) non-smokers (96%). A high proportion reported suffering from anxiety (26.8%) and depression (33.7%). Metabolic syndrome was identified in 34.9% of the sample. Conclusions The HealthTrack study sample was recruited to test the effectiveness of an interdisciplinary approach to preventive healthcare in self-identified overweight adults in the Illawarra region. The profile of participants gives some indication of those likely to use services similar to the trial design.