Limited evidence is available on the effectiveness of publicly funded weight loss (WL) clinics. We examined the 1-year WL outcomes and investigated predictors of WL and discontinuation of 1566 overweight and obese adults, who attended the Wharton Medical Clinic (WMC) weight management centre for at least 6 months. Overall, 42.7% (n = 669) of the entire sample achieved a ≥5%WL over the entire follow-up period from July 2008 to February 2012. On average, patients lost 5.6 ± 7.2 kg (5.0 ± 6.3%) of initial body weight (BW), while a subsample of patients attending the clinic for at least 1 year had a mean weight reduction of 6.6 ± 7.9 kg (5.9 ± 7.2%) of BW. Older patients were more likely to achieve a greater WL in comparison with young patients while White patients and those without type 2 diabetes (T2D) lost almost twice as much weight and %BW in comparison with Asian patients and patients with T2D, respectively (P < 0.05). Discontinuing patients did not differ in terms of sex, body mass index, education and smoking status from those who continued treatment (P > 0.05). Results of this study demonstrate that the WMC provides a practical model for clinically effective lifestyle-based treatment, accessible to a wide range of demographically diverse adults.