This week’s blog post is written by a guest writer, Janelle Wagnild
Stress causes us to crave and pursue large quantities of high-calorie foods, making it very difficult to stick to healthy eating habits. An evolutionary approach to understanding emotional eating can provide insights into how we can minimise the power food can have over us during stressful times.
Why do we crave high-calorie foods?
The foods that appeal to us the most, especially during times of stress, are usually high-calorie foods that contain lots of sugar, fat, salt, or a combination of those. It’s important to realise that we are not only wired to want these foods, but we are also wired to feel rewarded for eating them.
If we think way back in time to the pre-agricultural era of hunting and gathering, obtaining food was a day-to-day task with an unpredictable return. The easiest foods to find were often low in calories (e.g. leaves, roots, berries) and the high-calorie foods necessary for survival (e.g. meat, honey) required much more effort to acquire. To motivate us to pursue these foods, our physiology is programmed to launch a ‘reward’ system (a flood of dopamine in our brains) after consuming high-calorie foods rich in sugars, fats, and/or salt.
Today, we still carry this reward system in our bodies, but its purpose is undermined by our current food environments. Rather than this system encouraging us to find the calories we need to stay alive, this system makes it harder for us to resist the foods we don’t need. Our bodies still obviously require calories, but we (generally) have no problem getting access to sufficient calories (most of us have the opposite problem!). The system that was once required for survival now backfires since we’re surrounded by high-calorie options. Knowing that we’re wired to want these foods doesn’t necessarily make it any easier to resist them, but it’s comforting to know that there are evolutionary reasons these foods are so appealing!
Why does stress cause cravings?
Stress causes our cravings for these foods to be even more irresistible. When we’re stressed, our bodies produce a hormone called cortisol which makes us not only crave sugary foods, but also causes the body to metabolise those sugars really easily. This pathway has an evolutionary purpose: if, for example, you were faced with a threat of a predator, that stress would provoke you to seek out fuel and use it very efficiently when you needed the energy to run away from the threat. But when this ‘threat’ is a deadline at an office job, our bodies don’t necessarily recognise that we don’t need to be preparing to actually run. We’re prompted to find and consume sweets, but then we never end up needing to actually burn off what we consumed in preparation for the fight. Cue weight gain.
Why does binge eating help lower stress levels?
When we’re under stress, our bodies engage what’s called our sympathetic response (also called ‘fight or flight’). The sympathetic response is responsible for making our hearts beat faster, our blood pressure rise, and our sweat glands activate so that we’re ready to deal with imminent threats to our survival. This system serves an important purpose: it gives us energy to power through an all-nighter of work or enables us to run away from something that’s immediately endangering our lives.
In order to relax, our bodies have to switch from sympathetic mode to parasympathetic mode, the calm and relaxed opposite. This can be done by hitting the gym, having a glass of wine, or even by binge eating. Here’s why: our bodies are terrible at digesting food when in sympathetic response mode – if you’re running away from someone who’s trying to kill you, who has the time to leisurely digest a meal? Your body has more important things to do. But, if you flood your body with a large enough quantity of food, such as during a period of binge eating, your body is forced to switch out of sympathetic to parasympathetic (relaxed) mode in order to deal with digesting all of the food it’s received. In other words, binge eating actually physically calms the body just like a glass of wine or a warm bath does. This is not to say that binge eating is a good thing – it wreaks havoc on the body and contributes to weight gain – but it’s mechanistically no different than any other method of stress reduction. It has nothing to do with lack of self-discipline.
Understanding the physiology of food cravings and emotional eating is empowering. Many people resent the amount of control that they think food has over their lives because they need it to cope with stress. By recognising the functions of cravings and binging, however, the focus can be shifted away from diets and willpower to stress-reduction and self-care. By looking for alternative ways to calm down and unwind, emotional eating loses its power and helps bring food back to serving its intended purpose of simply fuelling the body.
Janelle Wagnild is a twice-published author with a Bachelor of Science degree in Applied Human Biology. She is currently a Master of Science in Evolutionary Medicine candidate at Durham University where she will begin her PhD work this fall.