It’s Not You, It’s Your Diet: How to Cultivate Body Trust by Understanding Hunger, Satiety, and Thirst
Have you ever felt “out of control” around food or wondered why you can’t lose weight? What if I told you it isn’t a lack of self-control that is to blame? Rather, what if I told you that you aren’t to blame at all! Would you feel a sense of relief or confusion? I remember when I first learned how diets were failing me, I felt utterly confused – so you mean I’m not actually a total failure? It’s not my fault that I’m fat? It took me a long time to fully comprehend the idea that my insatiable hunger was a direct result of my continued attempts to lose weight, and even worse, it was taking a toll on my mental and physical health. To help you understand how to cultivate body trust I want to start with the building blocks by explaining how hunger, satiety, and thirst function and then explain how dieting disrupts these functions.
One of those most important things to understand about hunger and satiety is that they are incredibly complex and involve sensory, metabolic, and neurochemical pathways which all interact with each other.1 To complicate things further, what we choose to eat and how much we choose to eat is also influenced by taste preferences and our environment which could include memory and past experiences.2 Researchers have been attempting to understand hunger and satiety for over a century and have proposed theories such as the stomach contraction theory, which was developed by Cannon and Washburn in 1912 and theorized that stomach contractions themselves caused feelings of hunger.2
The second most important thing to understand in regard to hunger and satiety, in my humble opinion, is evolution. Since I come from a background in Anthropology, the impact of evolution on human behavior has always been of interest to me. If we look at how humans evolved, it puts our drive to eat into perspective. In many ways, we are hardwired to overeat.1 When we look at human history, it’s clear that it was advantageous to overeat because food was scarce and famines were a real threat.1 Essentially, we’ve been programmed to survive famines. Humans that were able to consume more calories in a shorter period of time were more likely to survive and thus their genes were passed down.1 In the same vein, genes that supported the storage of fat were also advantageous.3 By simply taking a look back on human history we start to better understand our drive to eat. Weight-loss, which is so often touted as a “healthy” endeavor, goes against our innate biology.
Although humans are designed with an intense drive to eat, our bodies also have unique mechanisms in place to maintain homeostasis.3 One of the key mechanisms that regulate hunger and satiety in our bodies is hormones. Ghrelin, identified in 1999, has been coined the “hunger hormone” and is responsible for signaling to the brain that we are hungry.1 After Ghrelin does its job and we begin eating, the hormone Cholecystokinin (CCK) is released as the stomach and intestines start to stretch to accommodate food. CCK increases feelings of satisfaction, but it is not the only hormone responsible for satiety. GLP-1 and PYY, two other satiety hormones, are produced in the lower gut and have a more direct influence on satiety by sending messages to your brain that you have had enough.1 Lastly, to foolproof the system, the hormone Leptin is recruited to suppress appetite.1 These hormones have been identified throughout the literature as being key players in the regulation of hunger and satiety, but there are at least two dozen other hormones and peptides that may also play a role.1 To complicate things further, there are at least 40 receptor sites that have been identified as playing a role in the feelings of hunger and satiety and possibly 30 more that do.1
Research has explained a lot when it comes to hunger and satiety, but scientists are still unsure of why obesity continues to rise. Interestingly enough, Leptin is stored in the fat. So theoretically more body fat should mean more Leptin which doesn’t make sense when we look at obesity rates. There are several mutations that influence hunger and satiety that can explain some variance in BMI, but not all.1 One theory is that over time humans develop Leptin resistance and the appetite simply stops getting suppressed.1 Another theory is that the abundance of fat and sugar laden foods activates the brain’s reward center and essentially override satiety hormones by promoting food consumption.4 Science doesn’t fully understand the exact mechanisms behind our drive to overeat, but one thing that we do know is that it’s strong.
Now that famines are no longer a threat in the Western world and food is ample, our waistlines have started to increase, and dieting has emerged as a solution. So why isn’t your diet working? If we look at the ways dieting impacts hunger and satiety it becomes obvious that it’s not actually you that is failing, it is your diet that is failing you. In their book Body Respect authors Linda Bacon and Lucy Aphramor explain how dieting majorly disrupts our body’s internal regulation signals by mimicking starvation through caloric restriction. They explain that overeating after dieting is “a predictable physiological reaction” to this perceived starvation.3 This is because of the body’s strong desire to remain at homeostasis; once the body realizes fat stores are shrinking it will respond by trying to replace them through revving up appetite.3 Our bodies naturally adapt to what they perceive as a threat, and as a result our satiety response is weakened with yo-yo dieting.3
Hopefully a better understanding of these mechanisms cultivates more trust in your body to find balance when calories aren’t being intentionally manipulated. Hunger and satiety are second nature, but it’s the society we live in that manipulates how they function.
Let’s look at thirst to better understand this concept. Just like research on hunger, research on thirst has developed over time through many different theories. What we do know is that just like hunger, thirst is a biological mechanism meant to keep us alive. If we didn’t experience thirst, we wouldn’t drink water, and after we had lost 4 gallons through sweat and urination, we would eventually die. Similar to how hunger regulation works to restore homeostasis in the body, thirst regulation works to regulate water balance. The hormone angiotensin is a key regulator of thirst.2 When water is restricted, arterial pressure decreases and sodium concentration increases which gets detected by the kidney which then releases renin.1 When renin comes into contact with the blood, angiotensin is released which increases blood pressure and signals us to drink water.1 This entire process is going on without us even being conscious of it, and we don’t have control over it, so why would we expect to have control over our hunger? Understanding thirst in the context of hunger and satiety puts these mechanisms into perspective; why would we try to manipulate the systems that are maintaining balance?
Scientists are still working to understand the mechanisms that control hunger, satiety, and thirst. While a lot of research has illuminated the intricacies of our bodies’ ability to regulate itself, there is still much to be learned. For example, we understand that Leptin is a hormone that suppresses appetite, however, we can’t fully explain why Leptin resistance happens.1 It’s confusing to know, on a scientific level, that when we restrict calories our body responds by increasing hunger but also live in a society dominated by diet culture. The pressure to be thin and the desire to manipulate the way our bodies naturally want to be is something that can be investigated through a closer look at how we view fatness in the Western world. My hope with this blog post is that you understand, from a scientific perspective, that trusting your body is a much more sustainable practice than trying to go against our instinctual hunger and satiety cues by dieting.
References
1. Kluger J. The Science of Appetite. Time. http://content.time.com/time/specials/2007/article/0,28804,1626795_1627112_1626670,00.html. Published May 31, 2007. Accessed October 21, 2019.
2. Logue AW. The Psychology of Eating and Drinking. NY, NY: Routledge; 2015.
3. Bacon L, Aphramor L. Body Respect: What Conventional Health Books Get Wrong, Leave out, and Just Plain Fail to Understand about Weight. Dallas, TX: BenBella Books; 2014.
4. Sclafani A. Gut–brain nutrient signaling. Appetition vs. satiation. Appetite. 2013;71:454-458. doi:10.1016/j.appet.2012.05.024