Do you ever wonder how you know when to stop eating? It’s more than just the uncomfortable pinch of your waistband digging into your skin. Somehow your brain knows when you’re full.
Your hunger (or lack thereof) is regulated through homeostatic, sensory, and hedonic feedback. The first and most logical process is homeostatic regulation, which focuses on your energy balance. If there isn’t enough fuel in the body to make up for your energy expenditure, hormones called ghrelin and leptin signal a part of the brain called the hypothalamus to increase food intake and energy storage. At the same time, there are nerves in the gut that monitor the contents of the stomach and intestine. Stretch receptors will sense how full you are — literally. Like a hypothetical waistband telling your brain we’re reaching capacity as the stomach expands. Other neurons in the digestive tract will relay chemical cues to the brain, reporting on the nutritional value of your last meal. How much sugar did we have? What about fats? Did we get enough protein? What do we need more or less of?
Of course, if our eating behaviour was based on fullness and nutrition only, the entire dieting industry would cease to exist. It also totally matters how appealing your food is! The next system that signals from the body to the brain is the hedonic system, reporting on how palatable your food is. A slice of carrot cake with cream cheese frosting probably gets a yumminess score of 5/5, whereas just carrots alone would get a 2/5. Consuming food solely for enjoyment will trigger hedonic chemical signals: 2-arachidonoyl-glycerol (2-AG) and ghrelin! Studies have shown that these chemicals are consistently high in response to eating foods with “gustatory rewarding” properties. In fact, they make you feel like you want to eat when you see yummy food, even if you aren’t hungry. All of this feedback tells the brain how to adjust the appetite.
But there’s a difference between feeling full and when you actually stop eating. I, for one, know that all rules go out the window when I’m at an all-you-can-eat (AYCE) restaurant. I’ll go for seconds, thirds, and even fourths of sushi long after my ghrelin, leptin, stretch receptors, etc… all raise the stop sign. Why is that?
Well, eating patterns are also dictated by psychological and social influences. That’s how we distinguish between fullness and satisfaction with a meal. Being satisfied brings in a whole slew of other factors: was the eating experience enjoyable? Did the food taste how you hoped? Did you curb the craving you had? In simple terms: did that meal hit the spot? The process that decides when you stop eating is referred to by scientists as satiation.
A 2021 paper reported a “Satiation Framework,” which sought to define the factors that come into play to determine meal termination:
1. Planned Amount
3. Physical Satisfaction
4. Decreased Food Appeal
5. Decreased Priority of Eating
Notice how physical satisfaction, which refers to the processes discussed above, is only one out of five components that decide when you stop eating!
The planned amount refers to portion size and portion number. The first major influence on how much you eat is simply how much food you have. Eating chips from a family-size bag versus a snack pack makes your portion size much more variable. The eating context will influence this greatly; there’s much more personal control when serving your own plate at home versus pre-set portions at restaurants. It’s also why at an AYCE restaurant, you can request more and more servings, and end up eating more than if you ordered à la carte.
A multitude of social factors influence eating behaviour, which can be grouped into “self-consciousness.” People tend to decide what’s appropriate to eat based on others. It’s common to eat more when you’re around friends and family, whom you’re more comfortable with, and less in the company of strangers. A friend of mine went on a first date at an AYCE sushi restaurant and only ate 6 pieces of sushi! What a waste!
Food appeal and the hedonic system go hand in hand. While food preferences differ greatly from person to person, studies have shown that variety in your meals often results in increased appetite and consumption. The 50+ item menu at AYCE sushi is certainly motivation to go back for round two.
The last factor, “priority of eating,” is directly dependent on fullness and food appeal. If you’ve ever heard someone say, “I need to eat right now,” or “I’m so full but I want to eat more,” you’re witnessing their assessment of the priority of eating. As you make your way through a meal, the signals for physical fullness will start to decrease the priority of eating. Food with high appeal might keep priority high even when you know you should stop. On the other hand, if your only option is food you don’t like, you might find that you’re suddenly not hungry anymore.
All of these factors will influence individuals to different extents and will vary greatly from one social situation to another. More research should be done regarding social influences on eating behaviours, but it’s difficult to replicate these conditions in an experiment. Maybe we can’t study this in a laboratory, but I’d argue it’s a great case study for a sushi restaurant.