Chemical Myths #6: Alcohol makes you fat

On 720 ABC last week there were no fewer than two dietitians telling us that alcoholic drinks make you fat because they have a very high calorific content.
Unfortunately (or fortunately depending on how you look at it), this is not the case, and I’m frankly surprised that two people who should be experts in their field know so little about the chemistry of the human body.

You see, although alcoholic drinks do have a high calorific content, your body treats it as a waste product, not a fuel source.

We know this, as it is processed by your liver, not your muscles.

Consequently, the mechanism by which excess energy is converted to fat does not apply, as the energy is never released.

In other words, it’s the wrong type of fuel for your body.

Let’s have a look at how it all works.

Any fuel, whether it be food for your body, or petrol for your car, obeys this simple relationship:

Fuel + Oxygen = Energy + CO2 + water

In the case of petrol, for example, the equation is:

2C8H18 + 25O2 = 16CO2 + 18H2O + energy

For a simple carbohydrate, like glucose, the equation is

2C6H22O12 + 11O2 = 12CO2 + 22H2O

You will note with both processes, carbon dioxide is one of the products, and this is the source of the CO2 that we breathe out – it is simply the combustion product of the fuel that our body is running on.

Now, stated simply, the fuel that cars run on is petrol, and the fuel that the human body runs on is glucose.

If you put glucose in your car it wouldn’t run, and likewise, if you drank petrol it would make you very sick – it certainly wouldn’t be used as a fuel source by your body. And it shouldn’t surprise us that alcohol is in the same category as petrol, as it is also an automotive fuel.

So our body needs glucose to run. This is mostly supplied by the carbohydrates that we eat. Our body breaks them down from complex carbohydrates into simple carbohydrates, and we have our daily fuel source.

But this is also true if we are trying to lose weight. If we have a low carbohydrate intake, our body looks for other sources of fuel, and one of them is fat. But the difference between complex carbohydrates and fat is the rate at which the glucose is generated.

With carbs, it’s just like breaking a complex LEGO structure into individual blocks – very straightforward and rapid. But conversion of fat into glucose is a slow process, and this is why weight loss works best with processes that employ moderate exercise (like walking) instead of intense exercise, where there is not enough time for the fat conversion process.

But back to alcohol. Can alcohol be converted to carbs? Stated simply, the answer is no. It can be converted the other way of course, and this is how fermentation works – sugars are converted to alcohol. But the alcohol cannot be converted by your body back to glucose.

11140cookie-checkChemical Myths #6: Alcohol makes you fat

2 thoughts on “Chemical Myths #6: Alcohol makes you fat

  1. Hang on a second. Are we conflating “alcoholic drinks” with “alcohol”?

    I’m not a chemist, so I’m not going to argue with your case that alcohol may just spin through into elimination as a waste product through the liver.

    However the calorific content of alcoholic drinks is also due to the residual and added sugars present – which presumably would be metabolised in the usual way.

    The sources you highlight did refer to alcoholic drinks and not alcohol after all…

  2. Yes, certainly if there are sugars present they will have the same calorific effect as they would in any food, but the specific argument that was used in these segments was that since the alcohol (in alcoholic drinks) has a high calorific content it is fattening, and that is a false argument, for the reasons that I have outlined. One might just as well say that petrol is fattening, as it also has a very high calorific content (as any fuel would), but drinking petrol would not make you fat, but rather sick, as your body attempted to deal with the toxic chemicals.

    Incidentally, the word “intoxication” originally meant “ingesting a toxin” as that’s how your body regards alcohol – certainly not a source of energy

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