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Obesity increases NAFLD incidence in metabolically healthy individuals

Metabolically healthy obese individuals have an increased incidence for nonalcoholic fatty liver disease, according to data published in American Journal of Gastroenterology.

“These findings provide compelling evidence to support the hypothesis that [metabolically healthy obese] is not a harmless condition and that the obese phenotype per se … can increase development of NAFLD,” Yoosoo Chang, MD, PhD, of Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea, and colleagues wrote.

Chang and colleagues conducted a cohort study in 77,425 men and women without NAFLD and metabolic abnormalities at baseline, and followed them annually or biennially for an average of 4.5 years. The researchers defined being metabolically healthy as not having any metabolic syndrome component and having a homeostasis model assessment of insulin resistance (HOMA-IR) of less than 2.5.

During the course of 348,193.5 person-years of follow-up, 10,340 individuals developed NAFLD, with an incidence rate of 29.7 per 1,000 person-years.

The multivariable adjusted hazard ratios for incidence of NAFLD for patients who were underweight was 0.28 (95% CI, 0.24-0.33), 2.12 for overweight (95% CI, 2.03–2.22) and 3.47 for individuals with obesity (95% CI, 3.3–3.66).

In detailed dose–response analyses, increasing BMI from baseline showed a strong and linear relationship with the incidence of NAFLD, with no threshold at no risk.

The researchers noted that this strong association was present in both men and women, but stronger in women (P < .001). The absolute incidence rate of NAFLD was lower in women (15.5 per 1,000 person-years) compared with men (50.6 per 1,000 person-years).

In further analysis, researchers adjusted for multiple risk factors — fasting blood glucose, systolic blood pressure, HOMA-IR, LDL cholesterol, high-sensitivity C-reactive protein and HDL cholesterol — and found the association remained significant.  

“The association between BMI and incident NAFLD was strong and progressive, and was observed across the whole range of BMI values in all subgroups evaluated. … This association could not be explained by residual levels of metabolic risk factors below standard cutoffs used to define metabolic abnormalities,” the researchers wrote.

The researchers concluded: “Our findings indicate that excess adiposity is not a harmless condition and can induce the development of NAFLD even in subjects with no metabolic abnormalities.” – by Melinda Stevens

Disclosure: The researchers report no relevant financial disclosures.