I get asked a lot about alcohol and weight loss. Here’s a study which took a look at what happens to fat oxidation when alcohol is consumed (Siler SQ, Neese RA, Hellerstein MK. De novo lipogenesis, lipid kinetics, and whole-body lipid balances in humans after acute alcohol consumption. Am J Clin Nutr. 1999 Nov;70(5):928-36).
We used stable-isotope mass spectrometric methods with indirect calorimetry to establish the metabolic basis of changes in whole-body lipid balances in healthy men after consumption of 24 g alcohol.
Eight healthy subjects were studied and DNL (by mass-isotopomer distribution analysis), lipolysis (by dilution of [1,2,3,4-(13)C(4)]palmitate and [(2)H(5)]glycerol), conversion of alcohol to plasma acetate (by incorporation from [1-(13)C(1)]ethanol), and plasma acetate flux (by dilution of [1-(13)C(1)]acetate) were measured.
The fractional contribution from DNL to VLDL-triacylglycerol palmitate rose after alcohol consumption from 2 +/- 1% to 30 +/- 8%; nevertheless, the absolute rate of DNL (0.8 g/6 h) represented <5% of the ingested alcohol dose; 77 +/- 13% of the alcohol cleared from plasma was converted directly to acetate entering plasma. Acetate flux increased 2.5-fold after alcohol consumption. Adipose release of nonesterified fatty acids into plasma decreased by 53% and whole-body lipid oxidation decreased by 73%.
We conclude that the consumption of 24 g alcohol activates the hepatic DNL pathway modestly, but acetate produced in the liver and released into plasma inhibits lipolysis, alters tissue fuel selection, and represents the major quantitative fate of ingested ethanol.
It’s not so much that the alcohol itself gets turned to fat, it’s that alcohol inhibit lipolysis (fat burning).