Remember the food metabolism curve (Only Three Things in What We Eat)? That graph is only missing one thing. Alcohol.
The conventional wisdom (which seems to be repeated from Atkins) I have heard but now question is whether or not the body only burns alcohol if there are choices between alcohol and other things in the body. Alcohol is the best choice of all for the body in terms of ease of access so I wrongly concluded that the body puts off dealing with proteins, carbs and fats until the alcohol is metabolized.
The Atkins site (Q: Can I drink alcohol now following Atkins 40??) puts it this way:
The body burns alcohol for fuel when alcohol is available. So when it is burning alcohol, your body will not burn fat. This does not stop weight loss; it simply postpones it. Since the alcohol does not get stored as glycogen, you immediately get back into fat burning after the alcohol is used up.
Take careful note. They say that the body won’t burn fat but they don’t mention carbs or protein.
The truth is that the body burns all of the sources as best it can in some blended way. Some are more easily accessed than others and burn more quickly. Some are burned slower but all burn at the same time. Alcohol has it’s own curve for blood concentration (implicitly related to metabolism):
Also, Atkins can’t be right with the word “immediately” since this is such a long and smooth drop. What does make sense is that there are overlapping times when the alcohol level has reached a low enough point that the body has to start drawing energy from the stored energy sources. This isn’t a like a flipped switch at all.
Here’s some information on the interaction of Alcohol and other foods (Science here).
The concomitant ingestion of various foods with alcohol resulted in a decreased area under the blood alcohol concentration curve, a lower peak concentration and an increased time to reach peak. Michaelis-Menten kinetics indicated a decreased alcohol metabolism rate after the ingestion of carbohydrates or fats.
I think everyone who drinks realizes this (at least about carbs). If you eat food you get less drunk for both slower and longer. If you drink on an empty stomach you will get drunk faster but sober up more quickly. (PSA: Use those facts to whatever advantage you personally choose as long as you don’t drive. Find another way to stumble home than your car.)
However, that study does implicitly contradict the claim by Atkins. The study demonstrates that alcohol metabolism is reduced after the ingestion of fats. That implies to me that the body processes both at the same time. At least the dietary portion of the fat is still being burned. It’s not like the body puts the fat off into some corner and says that it won’t burn it until the alcohol is done. It does both at the same time. The alcohol acts slower but so do the other sources (Carbs, proteins and fats) just like they would in any other blended situation.
It is true that the body isn’t burning stored fat during that time, but that’s true of anything that a person eats. The body isn’t burning stored fat if it is getting enough energy from what you are digesting.
In fact the real story may be quite different. Take a look at the pathology of Alcoholic Ketoacidosis – a pretty serious condition (What Is Alcoholic Ketoacidosis?).
Cells need glucose (sugar) and insulin to function properly. Glucose comes from the food you eat, and the pancreas produces insulin. When you drink alcohol, your pancreas may stop producing insulin for a short time. Without insulin, your cells will not be able to use the glucose you consume for energy. To get the energy you need, your body will start to burn fat.
This is directly opposite of what Atkins says. At least for the alcoholic he has reached the point where his body is eating itself up by burning its own fat. That’s the exact goal of Atkins – to burn the body’s fat. The downside is that the blood glucose increases during that time. Note that this seems to take a lot of alcohol over an extended period of time but it does suggest that the alcohol itself does not prevent the body from burning fat.