Hunger, Satiety, and Thirst: Part 2
Last week I gave an overview of the many different factors that influence hunger. It's a complex subject, and I feel like I barely scraped the surface. However, this week I want to start a conversation about satiety. Satiety is defined as the suppression of eating between meals, and satiation is the "suppression of ongoing eating" (1) or the feeling that ends a meal.
In Part 1 of this series, we learned that insulin being released into the blood stream lowers blood glucose and can precipitate the feeling of being hungry. The body wants to refuel and raise blood glucose again. The glycemic index score elucidates the relationship between blood glucose, insulin, and hunger. Foods that have high glycemic index scores quickly raise blood sugar, which is quickly made low by insulin release. Remember, low blood sugar leads to hunger. Foods that have lower glycemic index scores do not cause this blood glucose and insulin release rollercoaster. Blood glucose stays stabilized, elongating the feeling of satiety and warding off hunger (2 p18-21). For example, if I ate a donut for breakfast, I would start feeling hunger a couple hours later. That donut caused a spike and subsequent drop in my blood glucose. However, a small bean and egg omelet for breakfast means I’m still satiated hours later.
The index is scored out of 100. Refined and processed foods tend to have higher scores (high glycemic index), while foods that are less processed and have more fiber have lower scores (low glycemic index). I am simplifying the concept of glycemic index because glycemic load could be taken into consideration too. That is the amount of glucose released into the blood stream per gram of carbohydrate consumed. It's something that is helpful for diabetics to understand. From what I've noticed, while many fruits have a high glycemic index, they also have a low glycemic load. Here are a few examples of foods at their glycemic index scores that I found in an article from Harvard Health Publishing (3). If you're curious, I recommend reading the article for more information regarding glycemic index v. load and what that may mean for blood sugar management.
- Instant oatmeal - 79
- White flour bread - 75
- Whole wheat bread - 69
- Coca Cola - 63
- Rice cakes - 82
- Low fat yogurt with fruit - 33
- Apple - 36
- Grapefruit - 25
- Hummus - 6
- Carrots - 39
I wouldn't rely on glycemic index alone to make food choices that promote satiety. For example, agave syrup was very popular in the health food world as an alternative to sugar because it has a low glycemic index. However, after the excitement died down, the health and wellness community realized that agave syrup is highly processed and extremely similar to high fructose corner syrup. It is no longer recommended as a sweetener (4).
Meals that contain fat, fiber, and protein come highly recommended by many NDs and nutritionists because those foods are known to promote satiety, in part because they do not cause spikes in blood glucose. They are considered "slow fuels" (5 p104). Fiber is especially important because it will slow down the digestion and absorption of carbohydrates and sugars in the food, thereby promoting stable blood sugar levels (5 p104).
The feeling of fullness is often attributed to the stomach stretching. There is something to this. Eating a plateful of broccoli is going to induce satiation better than a couple crackers because the broccoli is physically filling the stomach. However, this only works if what is consumed contains nutrients. Many people think that drinking a glass of water before a meal will help them feel fuller faster. That's not true. The water, while taking up space, doesn't have much for nutrients; and those people tend to eat more at a subsequent meal (2 p11,18).
A couple more chemicals produced by the body come into play when it comes to the cessation and suppression of eating: CCK and leptin. CCK is made in the small intestine and talks to the brain to promote the cessation of eating. The body will sense a "heaviness" in the stomach at the end of the meal, releasing CCK to stop eating. Additionally, low glycemic foods promote more release of CCK leading to greater satiety (2 p21-22, 26).
Leptin is produced by body fat and communicates with the brain as well. Generally speaking, the more body fat someone has, the more leptin he or she will produce. Recall neuropeptide Y? It is made in hypothalamus (in the brain) and increases the drive to eat. Leptin will communicate with the hypothalamus to counteract neuropeptide Y's signals, suppressing eating. For a while, researchers thought obese people are leptin deficient and giving them leptin would help them lose weight. Studies have shown that's unfortunately not the case for the majority of those who are obese. Something else is going on (7).
Distracted eating will likely lead to decreased satiety. Eating and only eating (no multitasking!), will lead to increased satiety. For instance, eating dinner while watching TV will increase the chances that later in the evening you'll want a snack too (2 p31). I am especially guilty of distracted eating, because I often eat while studying!
I hope you enjoyed learning about satiety! For further exploration into foods that increase satiety and stabilize blood glucose, I recommend reading Food as Medicine Everyday by Drs. Briley and Jackson. Look for a post next week for details about thirst!
1. Sclafani A. Gut–brain nutrient signaling. Appetition vs. satiation. Appetite. 2013;71:454-458.doi:10.1016/j.appet.2012.05.024.
2. Logue A. Chapter 2: Down the Hatch. In: The Psychology of Eating and Drinking. 4th Edition. New York, NY. Routledge; 2015: 11-32.
3. Glycemic Index and Glycemic Load for 100+ Foods. Available at: https://www.health.harvard.edu/diseases-and-conditions/glycemic-index-and-glycemic-load-for-100-foods. Published February 2015. Updated August 2015. Accessed February 13, 2018.
4. Hassell M. Section 1: Advice for Everyone. In: Good Food, Great Medicine. 3rd Edition. Hillsboro, OR. Lithtex; 2015. 8-58.
5. Briley J and Jackson C. Chapter 8: Balancing Blood Sugar. In: Food as Medicine Everyday. Portland, OR. NUNM Press; 2016. 101-110.
6. White W. Hunger, Satiety, Thirst. Psychology of Eating. January 2018.
7. Kluger J. The Science of Appetite. TIME. Available at: http://content.time.com/time/specials/2007/article/0,28804,1626795_1627112_1626670,00.html Published May 31, 2007. Accessed January 11, 2018.