Fat-free mass accounts for most of the variance in alcohol elimination rate in women

The rate at which women eliminate alcohol from their bloodstream is largely predicted by their lean body mass, although age plays a role, too, scientists have found. Lean body mass is defined as one’s total body weight minus fat. Women with obesity – and those who are older – clear alcohol from their systems 52% faster than women of healthy weights and those who are younger. The study is published in the journal Alcohol Clinical and Experimental Research.
Understanding how blood alcohol concentrations (BAC) achieved after drinking are determined is critical to predicting alcohol exposure to the brain and other organs and alcohol’s effects. However, predicting end-organ exposures is challenging, as there is wide variation in BAC achieved after drinking a specified volume of alcohol. Researchers assessed associations between obesity, fat-free mass (FFM), and alcohol elimination rates (AER) in women and examine whether bariatric surgeries, which are linked to an increased risk of alcohol misuse, affect these associations.
Data was analysed from three studies that used similar intravenous alcohol clamping procedures to estimate AER in 143 women (21 to 64 years old) with a wide range of body mass index (BMI; 18.5 to 48.4 kg/m2) and 19 of the women underwent bariatric surgery about 2 years before participation.
Obesity and older age were associated with a faster AER. Compared to women with normal weight, AER was 52% faster (95% Confidence Interval: 42% to 61%) in women with obesity. However, BMI lost predictive value when adding fat-free mass (FFM) to the regression model. Age, FFM, and its interaction explained 72% of individual variance in AER. AER was faster in women with higher FFM, particularly women in the top tertile of age. After controlling for FFM and age, bariatric surgery was not associated with differences in AER.
Obesity is associated with a faster AER, but this association is mediated by an obesity-related increase in FFM, particularly in older women. Previous findings of a reduced alcohol clearance following bariatric surgery compared with prior to surgery are likely explained by a reduction in FFM post-surgery.
Source: Seyedsadjadi, N., Ramchandani, V.A., Plawecki, M.H., Kosobud, A.E.K., O’Connor, S., Rowitz, B. et al. (2023) Fat-free mass accounts for most of the variance in alcohol elimination rate in women. Alcohol: Clinical and Experimental Research, 47, 848– 855.