This article was first published in The Skeptical Inquirer.
If you’ve never gotten fast food after leaving a bar late at night (or, more correctly, early in the morning) I’d highly recommend it. I’ve never been sure if it’s the intoxication, the tiredness, or the unusual hour that makes post-pub falafel taste like heaven, but somehow after I go out drinking with my lab mates the food always just is better. I had resigned myself to the mysterious joy of 2 a.m. poutine remaining just that, a mystery. But last Christmas my grandfather took me by the shoulders and with odd earnest asked me to write an article finding out if alcohol is an appetite stimulant. Well, Grandpa, it may have taken seven months, but here it is! Let’s take a look at the evidence for alcohol as an appetite stimulant.
While we don’t tend to think of alcohol as a source of energy, it does provide 7 kcal of energy per gram, making it more energy-dense than carbohydrates or protein (which are 4 kcal/g). Of macronutrients, only fats, at 9 kcal/g are denser. Of course, if you’ve ever glanced at the back of a beer bottle, you likely already know that alcoholic drinks can pack a serious caloric punch. Even if you avoid the sugars, flavors, and other ingredients in alcoholic drinks by having straight vodka, one jigger (1.5 fluid ounces) still comes in at almost 100 calories.
Now, thanks to the pervasive nature of the diet industrial complex, you’re likely already hyper-aware of the fact that alcoholic (and many nonalcoholic) drinks can contain large numbers of calories. Most diets start with advising their followers to stop drinking anything but water, coffee, or tea so that you’re not “drinking your calories.” This is a legitimate concern if you’re watching your weight, as studies have shown that your average adult can get up to 10 percent of their daily caloric intake just from alcohol. But beyond being simple sources of calories themselves, there’s good evidence that alcoholic drinks can affect your energy intake in a few different ways.
A big part of what makes the question if alcohol is an appetite stimulant so difficult to answer is the tremendous variety of alcoholic drinks. Some are bubbly, some are sweet, some are savory, some are more concentrated and others less so, and any of these aspects could inhibit or stimulate appetite. This compounds with all our associations and histories with certain drinks. For instance, you may associate red wine with good meals, and therefore be predisposed to eat more when drinking it. Maybe you eat less after drinking champagne because you associate it with New Year’s Day hangovers and get put off your meal. It could be that the carbonation in some drinks or the alcohol itself numbs your mouth and dulls your sense of taste. The point is, the effects of many of these parameters just haven’t been studied, and when they have been it has often been in studies lacking proper blinding and controls. What has been studied fairly extensively and with good scientific rigor are the effects of ethanol on appetite. Those studies and findings are what I will be discussing today.
There have been quite a few studies that have attempted to see whether alcohol is an orexigenic agent (the technical term for an appetite stimulant). They’re all slightly different in their experimental design, but the general idea is as follows: Give participants either an alcoholic or nonalcoholic beverage just before a meal and see how it affects how many calories they consume, how hungry they feel before, during, and after the meal, and how satisfied or full they feel after eating. The best-designed studies try to blind participants to whether they’ve received alcohol or not, but for obvious reasons that can be a bit difficult. The most common strategy seems to be to compare nonalcoholic beer to the same nonalcoholic beer spiked with ethanol so that the taste is as hidden as possible.
There is good evidence that alcohol makes us feel hungrier—but only once we actually start eating. In studies where participants were asked to rate their hunger throughout the experiment, researchers found increased hunger ratings once subjects had begun eating after drinking alcohol. In contrast, hunger ratings given before beginning eating, but after ingesting alcohol, were not increased. So, it seems that alcohol doesn’t increase hunger in general but rather increases hunger only once eating has begun.
It also seems that alcohol can reduce how satiated or full we feel after eating. A 2001 study of fourteen participants found that alcohol inhibits the secretion of leptin, a hormone that is partially responsible for inhibiting hunger and making us feel full. On the other hand, a 2005 study of eight subjects found that alcohol decreased the amount of ghrelin, commonly called the hunger hormone because it increases food intake, in the blood. So, the effects of alcohol on our fullness are likely complex and multivariable.
While lots of us have had a “liquid lunch” a time or two, it doesn’t seem that calories from ethanol produce the same fullness feelings as calories from carbs, fats, or proteins. Several studies have found no evidence that humans naturally modulate their eating habits to account for the calories consumed as alcohol. We’d expect (or maybe hope) that our bodies would show decreased hunger cues or increased fullness cues to account for the energy we already drank, but in studies, whether or not participants knew if they had consumed alcohol, they showed no signs of automatically regulating their calorie input. Because calories from alcohol don’t make us feel full like other calories, if we don’t keep careful track of our daily intakes, the calories from ethanol can easily be additive to the calories from our normal diets. This can lead to an excess of energy—and weight gain.
Because alcohol is so interwoven with our cultural traditions and daily lives, studies on how drinking affects hunger can be greatly influenced by expectation effects. We’ve come to associate drinking with eating, in particular with eating less healthy foods, and we commonly believe the idea that alcohol enhances appetite. This belief is so strong that in one study where participants consumed either alcohol-free beer (that they weren’t told was alcohol-free) or juice, their caloric intakes increased more after the beer. However, expectation effects alone are not enough to explain alcohol’s effects on appetite. Evidence of this is found in the same study. When participants were given alcohol (but not told they were receiving it) either in a drink they’d expect to be alcoholic (beer) or one they’d expect to be nonalcoholic (sparkling cranberry juice) their caloric intakes increased most when they didn’t expect the alcohol.
Perhaps you, like me, assumed alcohol led to us eating more simply because it lowers our restraints around eating. Interestingly, several studies have attempted to test this hypothesis and have not been able to prove it. As this 2010 review article concludes, “although alcohol has frequently been cited as a disinhibitor of restraint, the empirical evidence that the effects of alcohol depend on current restraint status is not strongly supported by the current literature.”
If we can circle back to my 2 a.m. poutine experiences for a moment, perhaps alcohol literally makes food taste better, leading us to eat more of it? There is a phenomenon known as the appetizer effect wherein eaters near the beginning of a meal will rate their hunger as higher if they also rate the food as yummier, or more palatable. Basically, this effect predicts that the yummier our food is, the hungrier we will feel when we first start eating it. Perhaps alcohol is contributing to this phenomenon and increasing how palatable we find foods. Fortunately, this is something we can test. Unfortunately, in studies that have taken palatability ratings from participants, no differences were found in the ratings between alcohol and control groups.
As with all research, these studies of alcohol and appetite can be influenced by confounding factors and unaccounted variables. These details can become especially important when interpreting the large-scale epidemiological studies on alcohol and BMI or appetite. Some studies have found a positive correlation between BMI or other measures of obesity and alcohol intake, while others have found that both not drinking and heavy drinking are associated with higher BMIs, while moderate drinking is not. Some studies that specifically looked at women have even found that high alcohol intake is associated with lowered amounts of body fat.
However, before you start planning your next diet as a seven-day bender, you should consider the many confounding variables that these studies may overlook. It may be that drink choice, drink frequency, binge-drinking, or totally unrelated factors such as sleep quality, dietary nutrition, or histories of eating disorders are influencing these results. Without further research, we simply cannot know for sure. I am pretty sure, though, that taking up heavy drinking in an effort to lose weight is a bad idea. If not for your waistline, then for your liver.
Outside of our diets, this research has some important implications in medicine. Appetite stimulants are commonly used to help treat anorexia resulting from cancer treatment or other medical procedures. They’re also quite commonly used in veterinary medicine to convince a sick animal to eat because although you may be able to convince a human who’s not hungry to eat anyway, good luck trying that with a cat. I can’t exactly imagine we’ll commonly see alcohol prescribed as an orexigenic drug, but an increased understanding of how alcohol affects our experiences of hunger and satiation can nonetheless lead to improvements in appetite stimulant research.
In the end, while we can’t be certain the mechanisms by which alcohol leads to increased calorie consumption or the effect size, the evidence certainly seems to indicate that it does. It appears that the munchies are no longer limited to cannabis consumers.