The broad takeaway is supported: recent U.S. evidence commonly places fatty liver in roughly 30% of adults, making “about one-third” a reasonable shorthand. The strongest support comes from national survey analyses and review articles showing prevalence near that level. The claim is not fully precise because estimates vary by definition and testing method, and many studies measure adults rather than all Americans.

The claim is well-supported. CDC NHANES data shows median body fat of 28% for men and 41% for women, meaning more than half of both sexes exceed 20%. Since obesity rates have only risen since this data was collected (1999–2004), the claim holds as a conservative estimate. However, 20% body fat is below the healthy range for women (21–33%), so exceeding it is normal and expected for most women — the claim is factually accurate but could mislead readers into thinking this threshold signals poor health for everyone.