While playing only a minor role in ethanol metabolism in average individuals, MEOS activity increases after chronic alcohol consumption.
It has delayed activity in non-chronic alcohol consumption states as increase in MEOS activity is correlated with an increase in production of CYP2E1, seen most conclusively in alcohol dehydrogenase negative deer mice.
[1] The MEOS pathway converts ethanol to acetaldehyde by way of a redox reaction.
[2][page needed] This process consumes ATP and dissipates heat, thus leading to the hypothesis that long term drinkers see an increase in resting energy expenditure.
[3] The increase in rest energy expenditure has, according to some studies, been explained by indicating that the MEOS "expends" nine calories per gram of ethanol to metabolize versus 7 calories per gram of ethanol ingested.