A few reason why consumtion of alcohol can wreck havoc on your health and your fitness goals

Alcohol suppresses fat metabolism. Whether calories from alcohol replace dietary calories or are added to normal caloric intake, alcohol suppresses fat metabolism by up to 30%.1 Another study showed a decline in fat metabolism by 73%.2

Alcohol occupies the liver so estrogen (produced in the body to balance testosterone production) cannot be processed so the two hormones “negate” each other.3

Alcohol depresses testosterone secretion. Exercise prior to alcohol intake can make the negative effects on testosterone secretion last longer by “direct inhibition at the testicular level.”4

Alcohol increases secretion of cortisol, which is catabolic. This may be one factor in alcohol-induced testosterone depression. Increased cortisol and decreased testosterone lasts up to 24 hours after drinking alcohol.5

Alcohol can depress nighttime HGH secretion by up to 70% (due to sleep disruption) and also spontaneous HGH secretion though the mechanism6 is unclear.

Alcohol interferes with post-exercise glycogen synthesis.7

Alcohol increases calcium excretion, which may reduce bone density, and magnesium, a mineral essential to energy production.

Alcohol is an appetizer, and impairs judgment so bad food choices are often made in the presence of alcohol.8

Alcohol irritates the GI tract and this may have a negative effect on nutrient absorption.

Alcohol has a diuretic effect, so it is dehydrating.