Beyond Weight Loss: Rethinking Dietary and Lifestyle Interventions for Liver Disease Modification in MASLD.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is commonly managed with dietary and lifestyle intervention, and weight loss is often used as a key marker of treatment success. However, changes in body weight alone do not fully describe the effects of lifestyle intervention on liver disease. This narrative review asks when lifestyle-induced changes can support a claim of liver disease modification. Current guidance generally associates sustained weight loss of at least 5% with reduced liver fat, 7-10% with reduced liver inflammation, and at least 10% with improvement in fibrosis. The review distinguishes weight loss from biological response, pathological improvement, and long-term clinical benefit. It considers how intervention exposure, biological response, outcome type, and duration of follow-up should be interpreted together. It also addresses differences in patient response, long-term adherence, and the limits of different study designs. Randomized trials, long-term observational studies, and target-trial emulation are considered in relation to what they can establish about causality and long-term benefit. We propose a five-question framework for evaluating lifestyle-induced liver disease modification: Who? What? Through which pathway? What outcome? For how long and with what evidence? Weight loss remains an important treatment target, but it should not be considered synonymous with liver disease modification. Claims of disease modification should reflect the level of evidence available. This framework provides a clearer way to distinguish short-term improvement from meaningful and durable modification of MASLD.