The Science & History Behind Eating

Most of us know which foods are considered healthy and nutritious and which are not. I mean, there are entire health and diet companies built on helping us change what we eat. Even as a nutritionist who knows all the rights and wrongs, I admit to still eating full pints of ice cream and reaching for another fry after announcing how sickly full I feel.  The struggle is all too real. So, why do we make the food and drink choices that we do when we know a plate full of veggies is most likely the better alternative? Most of it doesn’t stem from a lack of self-control but from the many factors that range from our physiology as humans to the food preferences we were conditioned to have from birth. (1) The factors that influence hunger, satiety, and thirst are vast, below is a brief, comprehensive look into the “why” of eating and drinking.


Regulated Hunger

Our bodies are well-oiled machines with the primary goal of keeping homeostasis, or a state of balance.  This balance includes temperature regulation, blood pH, glucose levels and a myriad of hormones. Hormones are regulated by the endocrine system which functions as the chemical messenger system in your body. (2)  This system is closely connected with the circulatory, nervous, immune and lymphatic systems and is also the system that tells our brain, to tell us, to go grab a snack.

Ghrelin is a hormone produced in the stomach when our blood sugar reaches a low point, when we see or smell a delicious dish, or most often when the clock strikes a regular meal time.  From the stomach, ghrelin travels to the brain which directs it to three particular areas: the hindbrain, which governs the body's unconscious processes; the hypothalamus, which is in charge of metabolism, and the mesolimbic center of the brain, where feelings of pleasure and satisfaction are processed. (3) In short, ghrelin tells you it’s time for lunch.

So, you eat lunch and ghrelin’s job is through.  The following hormones to roll in are the ones that stop you from eating four grain-bowls at once.  Cholecystokinin or CCK is produced in the upper small intestine during digestion and is triggered by pressure sensing, this hormone is the one responsible for the heavy fullness you feel as you finish your meal.  The following two hormones, GLP-1 and PYY, regulate overall energy balance by signaling the stomach to break down food and stimulate the pancreas to release insulin, which soaks up sugars released into the blood and regulates glucose. (4) Not to be left out of the hormone cocktail of hunger and satiety is leptin.  Leptin is an appetite suppressing hormone, that if it works well, is released by body fat in proportion to how much of the tissue you're carrying. (4)


Drink More Water

Like hunger, thirst is a sign to the brain that we must take action to stay in homeostasis. In thirst's case, homeostasis refers to regulating our plasma volume in the blood and electrolyte concentration. We’ve all heard that the human system is 75% water and by staying hydrated, we’re keeping our body running smoothly, eliminating toxins and maintaining cognitive function and alertness. (4) Just another reason to drink more water!

A Predetermined Love For Cookies

If our bodies are perfectly functioning machines designed to eat only when we’re hungry and stop when we’re full, where do overeating and weight gain come in? Blame should be pointed in the direction of our ancestors.  As human beings emerged, we were programmed to eat our fill when the food arrived, plus some. Not only that, we tended to favor fat, high caloric, and sugar-dense foods, as those were the foods with the highest energy value. (5)  So, we can thank our pre-industrial selves for the reward system in our brain that releases dopamine when we eat a sugary treat and then reach for another one. Luckily, our biologically predetermined food preferences aren’t the only factors we draw upon when choosing between a salad or burger. Our individual food story, or experiences with foods from prenatal to now, also influence daily food choices.

Most food preferences and aversions are learned through experience and cultural influences.  Meaning, our food story is heavily influenced by the culture we identify and were raised with as well as exposure to foods throughout life. From an early age, increased exposure to new tastes and experiences increases the likelihood of acceptance later on in life. (6) Moreover, this increased exposure will then increase an individual’s willingness to try new foods. Basically, if your parents made you eat your vegetables as a child, you’ll probably enjoy them as an adult and be more open to trying unfamiliar foods later on.

Cultural surroundings, economic status, food availability and marketing also influence our relationship with foods.  Making their way into our food choices are the knowledge, traditions, beliefs, values, and behavior patterns that are presented to us daily. (1)  For example, if you were raised in the Southern states, you might have a different idea of comfort food compared to an individual who grew up in Canada or India.  Similarly, cultures or individuals may choose to eliminate certain foods for religious, moral, or tradition based reasons.

In my opinion, eating should be a joyous experience and food is a message of love to our body. So, no matter the factors that bring you to your next meal, whether they're chemical, cultural or genetically pre-determined, the most important thing you can do is enjoy every nourishing bite.

food availability

Economic status and food availability should not be ignored as a limiting or expanding factor when making food choices. Whether it’s Whole Foods, the farmer’s market or the corner store, our exposure to foods is pre-determined by where we source it.


  1. Nutrition education: linking research, theory, and practice. - PubMed - NCBI. October 30, 2018.

  2. US EPA O. What is the Endocrine System? US EPA. July 6, 2015. Accessed October 27, 2018.

  3. Pradhan G, Samson SL, Sun Y. Ghrelin: much more than a hunger hormone. Curr Opin Clin Nutr Metab Care. 2013;16(6):619-624. doi:10.1097/MCO.0b013e328365b9be

  4. Cargill K. The Psychology of Eating and Drinking, Third Edition. Food, Culture and Society: An International Journal of Multidisciplinary Research. 2006;9:128-129. doi:10.2752/155280106778055226

  5. LoperHB, Sala ML, Dotson C, SteinleN. Taste perception, associated hormonal modulation, and nutrient intake. Nutrition Reviews. 2015;73(2):83-91. doi:10.1093/nutrit/nuu009.

  6. Wardle J, Cooke L. Genetic and environmental determinants of children’s food preferences. British Journal of Nutrition. 2008;99(S1):S15-S21. doi:10.1017/S000711450889246X