Habit-based interventions are a novel and emerging strategy to help reduce excess weight in individuals with overweight or obesity. This systematic review and meta-analysis aims to determine the efficacy of habit-based interventions on weight loss. We identified potential studies through electronic searches in February 2019. Included studies were randomized/quasi randomized controlled trials comparing weight loss interventions founded on habit-theory with a control (active or non-active) and enrolled adults with overweight or obesity (body mass index ≥ 25 kg/m 2). Five trials (630 participants) met our inclusion criteria. After the intervention period (range 8–14 weeks), weight loss was modest but statistically different between groups (1.4 kg [95% confidence interval 0.5, 2.3; P = 0.004]) favoring habit-based interventions. Intervention groups averaged 2.5 kg weight loss (range 1.7 to 6.7 kg) compared with control 1.5 kg (range 0.4 to 5.8 kg) and were 2.4 times more likely to achieve clinically beneficial weight loss (≥ 5% weight reduction). Average weight losses in adults with overweight and obesity using habit-based interventions appear to be of clinical benefit. There were statistically significant differences in weight loss between habit-based interventions and controls, post-intervention. Longer studies powered to examine at least 12-month follow-up are required to more accurately determine the role of habit-based interventions on long-term weight loss maintenance. Trial registration Prospero ID: CRD42017065589. Available from https://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42017065589.