Non-alcoholic fatty liver is commonly associated with obesity, but it is increasingly diagnosed in non-obese individuals as well. This study aims to investigate the prevalence of non-alcoholic fatty liver in non-obese individuals.

This is a systematic review and meta-analysis study that included data from datasets of PubMed, Scopus, Cochrane Library, and Scopus. The researchers identified 93 studies, 84 of which were used for prevalence analysis, five for incidence analysis, and eight for outcome analysis. The primary outcome of the study was the prevalence of non-alcoholic fatty liver in non-obese individuals.

The researchers found that the prevalence of non-alcoholic fatty liver disease (NAFLD) in non-obese individuals varied between 25 and 50%. The incidence of non-obese NAFLD was 24.6 among 1,000 person-years. The incidence of all-cause mortality was 12.1 among 1,000 person-years 4.1 per 1,000 person-years for liver-related mortality. The onset of hypertension in non-obese NAFLD patients was 56.1 per 1,000 person-years, and the onset of cardiovascular disease was 18.7 per 1,000 person-years.

The research concluded that around 40% of NAFLD patients were non-obese, and almost 20% of them were lean. Both lean and non-obese groups had significant liver and non-liver morbidities. The study also indicated that obesity should not be the sole criterion for NAFLD screening.