Theories of Hunger: Why Do We Eat?

· March 11, 2019
Discover the theories of hunger in this article!

It’s noon and you’re hungry. You feel even hungrier as the minutes pass. You need to eat now! However, you’re very busy at the moment, so you can’t. Now it’s four in the afternoon and you’re not hungry anymore. How many times have you heard phrases such as “I’m not hungry anymore”? There are many theories of hunger that point us to different answers to the question: why do we eat?

The answer may seem simple: because you’re hungry. But is that really the case? In part, yes, but why does hunger go away so many times? When you have your favorite meal, why do you eat more than you really need? “I’m not hungry anymore, but I love it”. And, just like that, you eat until you’re full.

Throughout this article, we’ll present the most popular theories of hunger that explain our eating behavior accurately and provide an answer to the previous question.

The set-point theory

The set-point theory attributes hunger to a lack of energySo, when you eat, you restore your optimal energy level. This is known as an energy adjustment point.

According to this theory, a person eats until they feel satisfied. At this point, they stop eating because they’ve restored their set-point. Therefore, eating has accomplished its function. As a result, this person doesn’t eat again until their body has expended enough energy to put it below the set-point.

The set-point systems consist of three components:

  • Adjustment mechanism: It establishes the set-point.
  • Detector mechanism: It identifies any deviations from the set-point.
  • Action mechanism: It’s a mechanism that eliminates the deviations.
A woman eating pasta.

All the set-point systems (Wenning, 1999) are negative feedback systems. In other words, the feedback that arises from changes in a certain direction produces compensatory effects in the opposite direction. We can usually find these systems in mammals and their purpose is to maintain homeostasis.

Now, if this theory was 100% true, once you reached your set-point, you’d stop eating. But this isn’t always the case, is it?

Glucostatic set-point theory

In the mid-twentieth century, several researchers believed that people ate to maintain their blood sugar level. This is the glucostatic set-point theory. In other words, you eat when your blood glucose level drops and stop eating when you restore it to normal levels.

Lipostatic set-point theory

According to this theory, each person has a body fat adjustment point. Therefore, people eat to recover this set-point.

Limitations of the set-point theories

The first limitation of these theories is that they don’t consider the influence of food flavor, upbringing, and social factors.

Such is the case of your favorite food or being in a social gathering. Imagine for a moment that your favorite food and another food that’s not as appetizing are on the same table. You probably aren’t going to eat a lot of the food you don’t like. However, you’re definitely going to eat a lot of the food you do like, even past the point of when you’re full. In other words, it’s possible to eat even when you’re not hungry.

Lowe (1993) stated that more than 50% of Americans have a significant excess of fatty deposits when they start eating. This fact also applies to people who have excess fatty deposits and continue eating nevertheless. Thus, this point also shows that set-point theories are incomplete.

Also, if these theories were exact, human beings wouldn’t have survived to this day. Pinel, Assanand, and Lehman (2000) stated that “The set-point theories of hunger and eating are inconsistent with basic evolutionary pressures related to hunger and eating as they are currently understood.”

The authors explained that our ancestors needed to eat a lot of food in case they couldn’t find any later on. Therefore, they would store calories in the form of body fat. If the set-point theory was exact, they’d have stopped eating once the deviations were restored. But if they had nothing to eat, they’d be left with no calorie reserves.

There are many theories of hunger to explore.

Positive-incentive perspective

According to the positive-incentive theory, humans and other animals are not normally motivated to eat by energy deficits, but are instead motivated to eat by the anticipated pleasure of eating, or the positive-incentive value (Booth, 1981).

“An empty stomach is not a good political adviser.”

-Albert Einstein-

This theory hypothesizes that hunger stems from the historical pressures we’ve suffered from the lack of food. So, rather than a lack of energy, what causes hunger is the presence of appetizing food or just the thought of it. 

Your hunger level depends on the interaction of different factors:

  • Flavor.
  • What you’ve learned about the effect of food.
  • The time that has passed since you had your last meal.
  • The amount and type of food you are currently digesting in your intestines.
  • Whether there are other people around or you’re eating alone.
  • Blood sugar levels.

Theories of hunger: Not everything is what it seems

In this overview of the main theories of hunger, we’ve seen that the answer to why we eat is not so simple. Something as common and regular as eating is not so easy to explain. This is because we don’t only eat when we’re hungry, but also because we like certain foods.

On the other hand, Jaime Silva (2007) emphasized that emotions and moods also influence food consumption. According to Silva, “On one hand, emotional states and moods can influence eating behaviorOn the other hand, food can modify emotions and moods.”

“Rice is great if you’re really hungry and want to eat two thousand of something.”

-Mitch Hedberg-

How many times have you eaten more than necessary to relieve your anxiety? Or how many times have you stopped eating because of it? Without a doubt, hunger has to be researched further.

  • Devoto, F., Zapparoli, L., Bonandrini, R., Berlingeri, M., Ferrulli, A., Luzi, L., … Paulesu, E. (2018). Hungry brains: A meta-analytical review of brain activation imaging studies on food perception and appetite in obese individuals. Neuroscience and Biobehavioral Reviews, 94, 271–285.
  • Espel-Huynh, H. M., Muratore, A. F., & Lowe, M. R. (2018). A narrative review of the construct of hedonic hunger and its measurement by the Power of Food Scale. Obesity Science & Practice, 4(3), 238–249.
  • MacCormack, J. K., & Lindquist, K. A. (2019). Feeling hangry? When hunger is conceptualized as emotion. Emotion , 19(2), 301–319.