Science 101

How Alcohol Affects Metabolism

The body metabolizes alcohol differently, and faster, than you might think.

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When it comes to the body and health, alcohol tends to play the villain. With metabolism, this narrative is no different, but it has a few surprising twists. Alcohol does, in fact, speed up your metabolism. When you consume alcohol, your body processes it first, before carbs, fats or proteins — technically, speeding up your metabolic processes compared to your baseline metabolism. But before you grab that bottle of Sancerre, consider the consequences. Like all science, it’s not so simple.

The Increase

In a notable study from 2003, published in The American Journal of Clinical Nutrition, researchers found that diet-induced thermogenesis (DIT) — the energy your body produces based on what you eat and drink — increased notably after an alcohol-rich breakfast compared to protein-, carbohydrate- or fat-rich meals. The alcohol-rich meal was a healthy breakfast with a screwdriver (orange juice with vodka) on the side. The conclusion: “intake of an alcohol-rich meal stimulates energy expenditure.” In other words, metabolism goes up. But the researchers also found that the alcohol-rich meal also suppressed fat oxidation and leptin (the “satiety hormone”).

The reason for the metabolic increase is that the body places alcohol in the fast lane. We cannot store alcohol, so the body breaks it down first. Metabolizing alcohol occurs with the help of two enzymes: alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). ADH metabolizes alcohol to acetaldehyde, then ALDH helps metabolize acetaldehyde to acetate, which is then metabolized into water and carbon dioxide, which is then expelled via breathing, sweat and urine. Still with us? The short version is: your body uses two enzymes to process the alcohol you consume, then expels it in the same way you do other nutrients.

The Side Effects

Everyone’s ADH and ALDH levels are different — some people break down alcohol faster than others. If you have a genetic disposition for fast ADH or slow ALDH — or if you’re simply consuming too much alcohol too fast, you may experience negative side effects, like facial flushing, nausea, and an increased heartbeat. A smaller liver and less body mass can also play a role — but anyone who has indulged in more Sancerre than they can handle knows there are side effects to speedy alcohol consumption. The body will try to metabolize alcohol as fast as it can, but it can only process so much. 

The side effects of alcohol consumption are where metabolism suffers most. People tend to eat more while drunk — lower inhibitions equals higher calories. And a recent study also found that alcohol can actually stimulate the appetite. A one-two gut punch.

Excess food consumption, especially large portions of calorie-dense foods consumed late at night, wreaks havoc on your metabolism, affecting your normal digestive rhythms. And when you consume alcohol, the body prioritizes the alcohol over other foods — carbs, fats, and proteins are put on metabolic hold. So although your overall DIT may be faster, you’re primarily processing something the body cannot store — meanwhile, the nutrients, which the body does store (as fat), are not being burned. You’re burning quick alcohol energy to clear it from the system while simultaneously storing the excess food energy that’s waiting in the digestive queue.

And when drinking, you sleep worse. As one review explains: “At all dosages, alcohol causes a reduction in sleep onset latency, a more consolidated first half sleep and an increase in sleep disruption in the second half of sleep.” And disrupted sleep leads to a whole host of issues, including disrupted metabolic processes.

In one final tipsy twist, exercise and alcohol are, surprisingly, positively linked — a review of current studies shows correlation in college students as well as the general population and across many types of drinking (heavy, episodic, etc.) and types of physical activity. So it’s possible that if you drink frequently, you also work out more — and exercise is positive for the metabolism. However, this is not information that should encourage drinking. In fact, it has been well established that alcohol consumption reduces protein synthesis and adversely affects both muscle recovery and future performance.

The relationship between alcohol and metabolism is complicated. Yes, it does speed up your DIT. And, yes, research suggests it may be likely that you’ll exercise more if you drink. But alcohol halts healthy processes like metabolizing food and entering sleep that tip the scales away from an efficient metabolism. In the end, the old adage is likely the most accurate. Everything in moderation — including the booze.

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