Prior studies in patients with severe obesity indicate that non-alcoholic fatty liver disease (NAFLD) exacerbates the risk of type 2 diabetes (T2D), and patients with coexistent NAFLD and T2D were more likely to have non-alcoholic steatohepatitis (NASH). However, remarkably low numbers of black patients in these reports limits the understanding as to whether the interconnections among severe obesity, NAFLD, and T2D are conserved across both races.


Liver biopsies were obtained during bariatric surgery in 224 adults with severe obesity; 156 white (45±11 years; 81% female; 46±6 kg/m2) and 68 black (43±12 years; 90% female; 49±7 kg/m2). Biopsies were assessed for presence and severity of NAFLD, NASH, and cirrhosis. Chi-square analyses were used to examine the interplay among race, severe obesity, NAFLD, and T2D.


Compared to whites, blacks were younger (p<0.01), heavier (p<0.01), and had lower incidences of both NAFLD (black: 34%; white: 62%, p<0.01) and NASH (p=0.01). The prevalence of T2D was similar between races (black:35%; white:38%, p=0.8) and did not differ when only patients with NAFLD were examined separately (48% both races). No between-race differences in fibrosis or cirrhosis were observed (p>0.4). When only patients with T2D were considered, a higher proportion of blacks (54%) than whites (22%) were free of NAFLD, and far fewer blacks (4%) than whites (28%) had NASH (p<0.01). T2D also coincided with greater fibrosis in whites (p<0.01), while differences in cirrhosis were not significant (black: 0%; white: 5%, p=0.5). Interestingly, whereas 66% of whites with T2D that required insulin had NAFLD, the five black patients on insulin were free of NAFLD.


Our findings question translation of the interconnections among severe obesity, NAFLD, and T2D observed in predominantly white bariatric surgery populations to black patients. Race likely has a profound impact on the pathophysiology and therapies for NAFLD and T2D.