Highlights • Data from 1,699 adult patients across 14 bariatric centres in the UK were analysed. • During the liver reducing diet, 30.6% of patients attained a >5% weight loss. • The optimal liver reducing diet is 800-1200kcals a day over a duration of 3-4 weeks. Abstract Background Liver-reducing diets (LRDs) are mandated prior to bariatric surgery, but there are no guidelines on their implementation. Objective To establish the variation and effectiveness of LRDs utilized in clinical practice.