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More recently, several studies compared NAFLD with MASLD. By definitions, in this case, the NAFLD-
only group is characterized by normal-weight individuals without signs of metabolic dysfunction; on the
other hand, few patients may be diagnosed with MASLD only if they have concomitant viral hepatitis
(which is not considered as an exclusion criterion in the MASLD definition). Importantly, the degree of
overlap between NAFLD and MASLD is even higher than between NAFLD and MAFLD, due to the
exclusion of significant alcohol intake in both definitions. For instance, in a recent study from Sweden on a
large cohort of patients diagnosed with NAFLD (most of whom have available data on liver histology), only
[74]
4 out of 1,333 (0.3%) did not meet the MASLD criteria . The Authors, therefore, conclude that no further
studies are necessary to evaluate the natural history of MASLD as it is superimposable to that of NAFLD;
similarly, given the high degree of concordance of the two definitions, there is no need to re-evaluate the
performance of noninvasive biomarkers of liver fibrosis compared with liver biopsy in patients with
MASLD . It should be noted, however, that these conclusions may not apply to different countries and
[75]
regions, especially those with a high proportion of lean NAFLD patients.

In a recent study performed using data from the 2017-2020 NHANES database (representative of the overall
US population), we showed that among participants with SLD, MASLD comprised the largest part (89.4%),
followed by MetALD/ALD (7.7%), with a very low proportion of participants falling in the cryptogenic SLD
category . In a subsequent study performed in South Korea, MASLD accounted for approximately 75% of
[76]
SLD cases, MetALD accounted for 20%, while 3.3% fell in the cryptogenic SLD category. Moreover, 95.80%
of the NAFLD cases fulfilled the new criteria for MASLD [77,78] . In general, studies performed in Asian
countries are more likely to identify participants with SLD that do not meet any metabolic dysfunction
criteria and, therefore, fall in the cryptogenic SLD category (i.e., that can be diagnosed with NAFLD but not
with MASLD). An interesting aspect of the new Delphi consensus is the introduction of a new disease entity
called MetALD, which represents patients with coexisting metabolic dysfunction, steatosis, and significant
alcohol intake. The introduction of this condition may represent a way to further study the impact of
alcohol on different outcomes in the setting of SLD [79,80] . In our study, these patients were characterized by a
higher FIB-4 score compared with patients with MASLD (as expected due to alcohol increasing the AST/
ALT ratio), while no significant difference was present in the proportion of patients with elevated LSM .
[73]
More recently, a few cohort studies evaluated the association between MASLD, MetALD, and hard clinical
outcomes such as all-cause mortality, cardiovascular events, and cancer-related mortality [81-84] . Most studies
were performed in general population settings and used either imaging or noninvasive scores to identify
steatosis. We summarized evidence from these studies in a systematic review and meta-analysis . Briefly,
[85]
compared with patients without SLD, both MASLD and MetALD were independently associated with a
higher risk of cardiovascular disease and all-cause mortality. Importantly, MetALD was also associated with
a higher risk of cancer-related mortality, while MASLD was not. Furthermore, Israelsen et al. showed that
the risk of liver-related events increased progressively from MASLD to MetALD to ALD, stressing the
[79]
importance of alcohol consumption on clinical outcomes throughout the spectrum of SLD .
Given that MASLD was recently introduced, studies comparing it to MAFLD are limited in number. There
are two main differences between these definitions. First, while MAFLD includes patients with significant
alcohol consumption, MASLD does not (as MetALD and ALD perform this task). Second, while both
include patients with overweight/obesity or type 2 diabetes, the main difference applies to normal-weight
individuals. While MASLD only needs one criterion for metabolic dysfunction, MAFLD needs two.
Therefore, when comparing the features of patients in non-overlapping groups, those with MASLD-only are
[86]
characterized by normal weight and a single metabolic abnormality . It is conceivable that these patients
(similarly to the NAFLD-only group) are at low risk for both liver-related events and cardiovascular
mortality. As the two definitions differ mostly in the number of metabolic abnormalities that need to be