In non-alcoholic fatty liver disease (NAFLD), steatosis can manifest through two distinct forms: macrovesicular (macroS) and microvesicular (microS).

To investigate the prevalence of microS and its association with biochemical parameters and NAFLD-related histological findings in individuals with obesity.

This is an observational retrospective cross-sectional study, enrolling individuals who underwent bariatric surgery and liver biopsy at a university hospital. A 1:2 propensity matching was performed to pair microS with isolated macroS; this matching enrolled variables “age,” “gender,” “body mass index (BMI),” and “obesity-associated medical problems.” Clinical, biochemical, and histopathological aspects were then analyzed and compared.

Of 115 participants, 88.7% were female; average age was 40.5 ± 5 years and mean BMI was 37.9 ± 3.3 kg/m². Steatosis occurred in 82.6% (67.8% isolated macroS and 14.8% microS). MicroS is significantly associated with higher levels of alanine aminotransferase (ALT) (39.8 ± 26.4 vs. 26.7 ± 17.5; p = 0.04) and glucose (103.8 ± 52.6 vs. 83.3 ± 10.8; p = 0.03) and higher frequencies of moderate to severe macroS (41.2% vs. 2.0%; p < 0.001), portal fibrosis (100% vs. 50%; p < 0.001), perisinusoidal fibrosis (100% vs. 55.9%; p < 0.001), lobular inflammation (100% vs. 41.1%; p < 0.001), and portal inflammation (100% vs. 41.1%; p < 0.001). An independently positive association was observed between intensities of microS and macroS (p < 0.001).

MicroS is significantly associated with higher levels of ALT and glucose and higher frequencies of moderate to severe macroS, hepatocellular ballooning, portal fibrosis, perisinusoidal fibrosis, lobular inflammation, and portal inflammation. These findings indicate that microS could be considered a reliable histological marker of NAFLD severity.