Picture this: feet aching and clothes soaked in sweat, you stumble out of Revs. Your friend suggests a trip to Maccies and you pounce at the chance. I’m salivating just thinking about it. Now imagine your friend announces they want salad. Yeah… no. Not happening. Personally, I’d look them up and down before telling them they are not in their right mind. So what is it that makes fast food so appealing after a night out?

In science, the term ‘alcohol’ refers to a family of organic molecules containing an -OH group. The substance found in alcoholic beverages given the colloquial term ‘alcohol’ is ethanol (C₂H₅OH), the only member of this group that we are able to drink.

From what I’ve gathered, there are three main reasons we might experience fast-food cravings after a few drinks:

1. Inefficient energy production from alcohol

2. Alcohol’s effects on the homeostatic system

3. Alcohol’s effects on the hedonic system

Out of the many foods we eat, alcohol is the least satiating macronutrient. However, out of the macronutrients, it is broken down and metabolised the fastest, through a process known as oxidation. Since alcohol cannot be stored in the body, it must be eradicated as soon as possible, so its metabolism is prioritised. This suppresses oxidation of fats and carbohydrates, which are more efficient sources of ATP, the molecule made by mitochondria that cells use for energy. This decreased rate of energy production when breaking down alcohol leads to your body searching for more calorie-dense foods to compensate, whether that’s a Double Big Mac or cheesy fries from Gardies.

“This decreased rate of energy production when breaking down alcohol leads to your body searching for more calorie-dense foods to compensate”

The other two reasons are related to the fantastic decision making skills we acquire whilst drunk. There are two systems that regulate feeding behaviour and maintain energy balance: the homeostatic and the hedonic system. The homeostatic system refers to the metabolic mechanisms mentioned above as well as signalling molecules known as hormones. The key hormones modulating feeding behaviour are ghrelin, insulin, and leptin. Ghrelin is responsible for stimulating hunger, while increases in insulin and leptin indicate satiety. The consumption of alcohol decreases the production of leptin, preventing it from suppressing hunger in the hypothalamus, meaning you can’t recognize you’re full. In addition, alcohol increases ghrelin levels to promote appetite. This combined effect drives overeating of calorie dense foods.

“Alcohol also suppresses pro-opiomelanocortin (POMC) neurons, a type of cell in the hypothalamus which reduce appetite”

These hormones then affect the second system modulating feeding behaviour: the hedonic system. This is the body’s reward system, which can override the homeostatic system to stimulate feeding behaviour. The hormones mentioned above, as well as galanin produced by the hypothalamus, act on the neural circuits in the hypothalamus and hindbrain that make up the hedonic system. In particular, the effect of increased galanin production through the consumption of alcohol stimulates cravings for fatty, calorie-dense foods. Alcohol also suppresses pro-opiomelanocortin (POMC) neurons, a type of cell in the hypothalamus which reduce appetite, caused by the decrease in leptin and insulin (as mentioned above). On the flipside, alcohol stimulates a group of cells called NPY/AgRP neurons, which antagonise POMC activity.

To summarise, we are driven to Maccies by the need to maintain a certain level of energy production and the overwhelming change in the level of hunger and satiety hormones that follows a dose of ethanol. However, it must be mentioned that other factors such as habits and conditioning, social cues, and the proximity of fast-food chains to Mash all play a role in influencing consumption. Anyway, if the science doesn’t persuade you, at least you have to agree that you appreciate a chance to sit down from all that dancing!

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