Expanding these findings, a recent study explored the relationship between body composition and AER in females, also using the intravenous alcohol clamp (116). The study found that females with obesity had a 52% faster AER than those with normal weight (116) (For an example of AER for individuals with different BMI, see Figure 8). The investigators controlled for these factors and indeed found that most of the association between obesity and AER was dependent on fat-free mass (FFM), consistent with earlier observations that individuals with obesity tend to have more FFM than those of the same sex, age, and height without obesity (208). Specifically, age and FFM together accounted for 72% of the individual variation in AER. Given that FFM strongly predicts lean liver volume— the functional portion of the liver involved in drug metabolism— (207) the dependence of AER on FFM likely reflects the robust relationship between FFM and liver volume, a major determinant of AER (206, 207, 209).
