Have you ever felt super full after eating a low-calorie meal, or still hungry after eating a calorie dense one? This has certainly happened to me; for example, one day last week I just ate carrots and drank a bit of cold-pressed juice and felt extremely full all day, yet the following day I had three pieces of pizza and three mozza sticks (all made with a high-fat vegan cheese) and still felt hungry afterwards.
How does this make any sense whatsoever? Contrary to popular belief, it’s because our stomachs don’t get filled up as quickly when we eat high calorie foods like meats and oils as they do when we consume more nutrient-dense, lighter foods like fruits and vegetables. This happens because of how our stomach receptors and nutrient receptors work.
How Our Stomach Receptors Determine That We’re Full
Many people seem to be terrified of raw food diets because people on plant-based diets tend to eat more food. However, have you ever actually seen someone gain weight by eating a plant-based diet? Odds are that you haven’t, because they’ve cut out high calorie foods like meat, dairy, and on some occasions, oil. In reality, people on plant-based diets typically lose weight because, even though they’re eating more volume, they’re getting far more nutrients and eating far fewer calories (source).
In our stomachs, we have nutrient (or caloric) sensors and stretch receptors. Most of the calories found in a typical North American diet are made up of animal products and processed foods, meaning that most people are severely nutrient and fiber deficient. If your diet doesn’t have enough plant-based foods in it and you’re not getting enough nutrients, your body will continue to feel hungry until those needs are met. Plus, high-fat foods and sweets dull our dopamine reward system, leaving us feeling unsatisfied, even if we’ve just consumed a high-calorie meal.
It’s kind of beautiful because your body is literally telling you that you aren’t feeding it what it wants. Your body will actually communicate with you — all you have to do is listen. Stretch receptors will also send a signal to our brains, telling us the stomach is full, but they only send these messages once our stomach has enough bulk or volume in it. Fiber is what provides the most amount of bulk, something that processed foods and animal products lack, whereas plant-based foods are rich in it. This concept is also known as “volumetrics,” a term coined by Barbara Rolls, Ph.D., a nutritionist at Penn State.
For example, the following diagram by Julianna Hever illustrates what 400 calories in our stomach looks like depending on what types of food we’ve consumed: