The Effects of Alcohol


It is no surprise that alcohol impairs mental and physical functioning, and that it is a depressant. Many people are also aware that alcohol is fattening, but the reason is less well known. The reason why alcohol is fattening is due to its effects on the Krebs cycle which are profound. The consequences are far reaching and some of these effects remain long after alcohol is no longer present in the system. Although the negative effects of alcohol are many, this article will focus primarily on those that affect fat loss and fat gain.


One of the important facts about alcohol is that it cannot be stored and therefore must be metabolized. The body begins this process by breaking down the alcohol into Nicotinamide Adenine Dehydrogenase (NADH) and acetaldehyde. After that, the body must then metabolize both of these substances. Unfortunately, the NADH and acetaldehyde are produced at a greater rate than which the body can metabolize them. In addition, some of the alcohol escapes into the blood stream unchanged.


The liver metabolizes acetaldehyde by converting it to acetic acid, and then to water and carbon dioxide in the Krebs cycle. However, because the production of acetaldehyde usually exceeds the liver's ability to metabolize it, much of it ends up in the blood stream. This rapid buildup of acetaldehyde is primarily responsible for the harmful effects of alcohol. The presence of acetaldehyde inhibits the Krebs cycle in the mitochondria and can cause the following conditions:

1. It will slow down the metabolism by reducing aerobic lipolysis (fat burning) and aerobic glycolysis. This will force the body to use primarily anaerobic pathways such as anaerobic glycolysis, which can result in lactic acid buildup.

2. Since conversion of lactic acid back to glucose (gluconeogenesis) often requires aerobic lipolysis to support the reaction (see related article), the absence of this reaction can lead to excessive lactic acid buildup (lactic acidosis) as well as hypoglycemia (low blood sugar).

3. Because acetaldehyde can only be destroyed in the Krebs cycle (which is disrupted due to its presence), greater concentrations of acetaldehyde will reduce the rate at which the body can destroy it. If acetaldehyde is still being produced due to continued alcohol consumption, then this will lead to a vicious cycle that will aggravate the previously mentioned problems.


The production of NADH from alcohol does have some effects that can affect fitness and fat loss programs. NADH gives alcohol a caloric value of about 7 calories per gram. Also, because the body has no metabolic requirement for alcohol, all of these calories are empty calories. This will force the Krebs cycle to burn off these calories instead of burning fat. Since the Krebs cycle is inhibited by the acetaldehyde that is present, these empty calories will quickly accumulate and force the body into a state of lipogenesis (fat production). In addition, NADH increases the rate of conversion of pyruvic acid to lactic acid which leaves less pyruvic acid available for conversion to glucose. When this is combined with the effects of acetaldehyde, it will aggravate the excess lactic acid buildup and increase the risk of hypoglycemia. Both of these conditions will degrade energy levels and athletic performance.


In summary, alcohol contains about 7 calories per gram. This is a high caloric density which is second only to that of fat itself. Also, all of these calories are empty calories which will either prevent you from burning fat, or will be turned into fat. It also induces hypoglycemia and excessive lactic acid buildup, both of which make it difficult if not impossible to exercise. There is no question that alcohol is one of the most fattening substances that a person can consume.