Despite the significance placed on lifestyle interventions for obesity management, around 40% of weight loss is regained over the first year following treatment, and much of the rest over the next three years. Two psychological concepts (habitual behaviour and automaticity) have been suggested as the most plausible explanations of this overwhelming lack of long-term weight loss success. We evaluated the efficacy of two interventions that explore these theories: Ten Top Tips (10TT) and Do Something Different (DSD). 10TT promotes automaticity; this is the ability to perform tasks without awareness or deliberation. Conversely DSD promotes behavioural flexibility by disrupting daily routines which subsequently promotes mindful behaviours. Both interventions have achieved significant weight loss with results suggesting potential for maintenance of the weight lost. The research however is limited and long-term (12 month) results are yet to be explored. Participants (n = 75), aged 51 ± 6 (s.d.) years with BMI 34.5 ± 4.1 kg/m² were randomised to 12-week 10TT, DSD or no treatment control and followed up for 12 months. After the 12-week intervention, weight loss averaged 4.6kg in the 10TT group, 4.1kg in the DSD group and 1.3kg in the control group. There was significant improvement in wellbeing in the 10TT and DSD groups. At 6 month no treatment follow-up there was a further weight loss of 0.2kg in the 10TT group and 0.9kg in the DSD group. Results from this RCT have the potential to help in understanding the mechanisms relating to weight loss maintenance.