BACKGROUND: Metabolic dysfunction-associated steatotic liver disease (MASLD) affects up to 30% of Western populations. While obesity is a recognized risk factor, MASLD does not develop in all obese individuals, highlighting the need to understand genetic and environmental interactions. The PNPLA3 I148M variant has been identified as a key genetic risk factor, significantly increasing the likelihood of MASLD development and progression. METHODS: We reviewed current literature on the role of PNPLA3 I148M in MASLD, focusing on gene-environment interactions involving diet, physical activity, obesity, and insulin resistance. We included studies analysing ethnic differences in PNPLA3 I148M prevalence and its association with MASLD. Additionally, we reviewed data on how PNPLA3 I148M influences the response to therapies, including lipid-lowering medications and GLP-1 agonists. RESULTS: The PNPLA3 I148M variant markedly heightens MASLD risk, particularly in Hispanic populations, where a higher prevalence of MASLD is observed. Lifestyle factors such as high sugar intake, alcohol consumption, and physical inactivity exacerbate MASLD risk among I148M carriers. Evidence shows that insulin resistance amplifies MASLD risk associated with the I148M variant, especially in non-diabetic individuals. Moreover, the PNPLA3 I148M variant interacts with other genetic loci, further modifying MASLD risk and disease course. The variant also influences treatment response, with variability observed in effectiveness of lipid-lowering therapies and GLP-1 agonists among carriers. CONCLUSION: The interplay between PNPLA3 I148M and environmental factors underscores the need for personalized MASLD prevention and treatment strategies. Targeting both genetic and lifestyle contributors may enhance MASLD management, offering a tailored approach to reducing disease burden.