Global NAFLD Rates Are High in Patients With Overweight and Obesity

More than two-thirds of individuals with overweight and obesity globally have nonalcoholic fatty liver disease (NAFLD), according to a study in The Lancet Gastroenterology & Hepatology.

Researchers conducted a systematic review and meta-analysis to estimate the global prevalence of NAFLD, nonalcoholic fatty liver (NAFL), and nonalcoholic steatohepatitis (NASH) among patients with overweight and obesity. A search was performed in the Medline and Embase databases for original articles, including cross-sectional and longitudinal observational studies.

The primary outcomes were the prevalence of NAFLD, NAFL, and NASH in the overweight and obese population and fibrosis in the overweight or obese population who had NAFLD.

Overweight was defined as having a body mass index (BMI) of at least 25.0 kg/m² in the general population and a BMI of at least 23.0 kg/m² for Asian individuals. Obesity was defined as having a BMI of at least 30.0 kg/m² in the general population and a BMI of at least 27.5 kg/m² for Asian individuals.

A total of 151 studies with 101,028 individuals (49,171 with NAFLD and 51,857 without NAFLD) were included in the meta-analysis.

In the pooled analysis, the prevalence of NAFLD in the overweight population was 69.99% (95% CI, 65.40-74.21; I²=99.10%). The prevalence of NAFL in this population was 42.49% (95% CI, 32.55-53.08; I²=96.40%), and the prevalence of NASH was 33.50% (28.38-39.04; I²=95.60%).

In a sensitivity analysis of individuals with obesity, the prevalence of NAFLD was 75.27% (95% CI, 70.90-79.18; I²=98.50%), the prevalence of NAFL was 43.05% (32.78-53.97; I²=96.30%), and the prevalence of NASH was 33.67% (28.45-39.31; I²=95.60%). The prevalence of NASH in individuals with obesity with NAFLD was 44.05% (95% CI, 37.42-50.90; I²=96.10%).

Among all individuals with overweight, the estimated NAFLD prevalence was 59.69% (95% CI, 53.51-65.57; I²=99.00%) in Asian and Middle Eastern countries or territories and 75.00% (69.28-79.96; I²=99.00%) in European countries and countries in North and South America.

In a subgroup analysis that stratified prevalence according to the geographical regions defined by the World Health Organization, the prevalence of NAFLD in the overweight population was the highest in the Americas (75.34% [95% CI, 67.31-81.93]; I²=99.00%).

Among individuals with overweight with NAFLD, 20.27% (95% CI, 11.32-33.62; I²=93.00%) had clinically significant fibrosis (stages F2-4), and 6.65% (4.35-10.01; I²=58.00%) had advanced fibrosis (stages F3-4). In addition, 21.60% (95% CI, 11.47-36.92; I²=95.00%) of individuals with obesity with NAFLD had clinically significant fibrosis (stages F2-4), and 6.85% (3.85-11.90; I²=90.00%) had advanced fibrosis (stages F3-4).

In a pooled analysis of individuals with overweight and obesity with NASH, the prevalence of clinically significant fibrosis was 35.14% (21.90-51.15; I²=91.00%), and the prevalence of advanced fibrosis was 19.35% (7.61-41.11; I²=77.00%).

In several noted limitations, the analysis included only articles that were written in or translated into English. In addition, the summation of NAFL and NASH events does not total 100% owing to statistical weighted pooling and selection of articles, and valid estimation of pooled disease prevalence requires inverse probability weighting based on population data. Also, the selection criteria of tertiary centers can confound the results, and the study was unable to account for other risk factors associated with NAFLD in individuals with overweight and obesity.

“Obesity is a well-known risk factor associated with NAFLD and these findings could be pivotal in improving the stratification of the disease burden for future early clinical intervention in overweight and obese individuals, especially at the level of primary care,” the study authors wrote.

Disclosure: Some of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.