Satiety, by definition, refers to an individual’s state in terms of being full. More specifically, when someone feels sate or satiated, it means that he has satisfied his cravings to the max while feeling full. So, while satiety does not exclusively mean full, it could be said so when it comes to the topic of diet and nutrition. This leads us to talk about satiety index.
What is the satiety index?
The satiety index refers to a chart that was created by Dr. Susanna Holt at Sydney University in Australia who conducted a clinical study to observe the different filling effect of different foods on hunger. In Holt’s study, the researchers team fed 11 to 13 individuals pre-fixed portions of food that had a caloric content of 240 calories. However, the individuals were fed foods from different food groups such as: fruits, vegetables, protein-rich foods, breakfast foods and carbohydrate-dense foods.
White bread was used as a base measure of the satiety of other foods.
The researchers set the value of white bread’s satiety index at 100%, thus, when the other foods satiety index was calculated, they were measured in percentages in relation to white bread. The researchers calculated the satiating effect of foods by asking individuals if they felt hungry every 15 minutes after their meal over a 2 hours’ period. The individuals were also instructed that they can eat whenever they felt like it, however, they were observed to see who felt hungrier first.
What the heck does all of this mean to us?
This means that the researchers wanted to see which foods will fill humans the most while having the lowest number of calories, period.
Results of the study were as follows:
As you can see in the picture above, potatoes were indicated to be the most satiating food compared to the other foods. Croissants scored the lowest and popcorn was up there as well. Keep in mind that this data is based on individual perception of hunger and 240 caloric portions of different foods, thus, the only factor those foods had in common was the number of calories they contained.
Limitations of the study
While this is a great study that set the path for a new branch of food and nutrition research, more studies should be conducted to further elaborate different aspects of satiety in individuals, especially those who are striving to lose weight or change their body composition.
Anyway, the study in hand has some detrimental limitations that could’ve skewed the results in both directions.
Individuals weights: The study did not take into account the different weights of individuals. Different individual weights mean different caloric requirements, thus a 200 pounds’ individual will not feel full or satisfied by a stupid 240 calorie food portion, however, in relation, a 150 pounds’ individual will most likely feel more satiated by the same food portion.
Physical activity: Were all the individuals physically active? Were some of them physically active while the rest weren’t? Individuals who perform regular physical activity will always require more energy and nutrients, thus their bodies will need more food. I am sure a 240-calorie food portion won’t do the trick. In fact, even those who perform more physical activity due to lifestyle or a physically demanding job will need more energy.
Perception of hunger: Perception of hunger is a very subject factor that could’ve skewed the results. Due to different known and unknown physiological and psychological reasons, I may feel full by a 200-calorie snack, while you may not!
Food choices: Once again, the food choices the study had given the individuals could’ve skewed the results due to individual differences in food preferences and cravings, both are subjective elements. You may like chocolate and feel satiated by 3 cubes, while another person might despise chocolate (those individuals don’t exist ha!) and would never eat it even if his life depended on it. In fact, anecdotally, I have an uncle who can eat raw vegetables and enjoy every bite, however, if you give him a salad made by the same ingredients he likes, he cannot eat it for some reason and if he forces it down, he feels sick! Why that is, no one knows.
Leptin sensitivity: Leptin is a hormone secreted by adipose cells that has a major effect on regulating hunger. Leptin is also known as the satiety hormone because it sends signals to your body when you are full. Just like other hormones, leptin has a sensitivity factor and individual differences come into play here. For instance, in obese individuals, leptin’s sensitivity is skewed and the body cannot accurately determine how full the body is despite of high energy (fat) stores. Thus, skewed leptin sensitivity could’ve affected the research subject’s perception of hunger.
Ghrelin sensitivity: Ghrelin is another hormone related to hunger. Ghrelin is the counteracting hormone of leptin, thus is makes someone feel hungry. In this study, differences in individual ghrelin sensitivities could’ve skewed the results by making an individual feel hungrier than he should’ve. Good thing is that ghrelin also makes your body secrets more growth hormone ;).
Metabolism level: How were the individual differences in metabolic functions? Were they the same? Probably not. A skinny person with a fast metabolism and another person with a slower metabolism will perceive hunger differently.
Psychological factors: Different psychological and emotional states can affect peoples’ eating behavior and thus their hunger perception. Anecdotally, most people do not want to eat when they are sad or depressed, while others feel the opposite way. Same goes for when we are happy. How were the emotional states of the research subjects?
Physical activity: In addition, did one of the subjects perform some sort of physical activity before going through the study? If an individual did so, he will most likely want to eat more food relative to the other subjects who did not perform any activity prior to the study. Well, I guess the world will never know.
Caloric deficit: Due to a multitude of physiological and psychological reasons, individuals who are in a caloric deficit will experience more hunger than those who don’t. If a few of the subjects were in a caloric deficit and the rest weren’t, that might have skewed their hunger perception and feeling of satiation.
Fasted state: If it happens to be that one of the individuals was in a fasted state, won’t he want to eat more food? I think so…
This is not to say that the study in hand was not beneficial or it is a piece of crap, however, this is just to point out different elements that could’ve skewed the results. More research that covers the aforementioned limitations should be performed. Nonetheless, this study is still a good piece of research and a foundation for the satiety index. Point is, this will help us design the optimal diet plan!
Why are certain foods more satiating than others?
This leads up to the following question, why are some foods more satiating that others?
I have seen numerous sites state different things in regards to what makes a food satiating, and quite frankly, they all either speculate or provide lacking information. There are many factors that make a food more filling and pleasing, some are biological and some are subjective, let’s have a look at them.
Volume: volume of food refers to how much of the food is there. For example, 200 grams of lettuce will not be as voluminous as 200 grams of steak. The volume of 200 grams of lettuce will be much more than the 200 grams of steak and will occupy more space for lower calories.
Caloric density: extrapolating on my last point about volume, different foods will have different caloric densities. For instance, 100 grams of lettuce have 15 calories while 100 grams of cookies will have more than 150 calories! That is 10 times more the calories. I think lettuce wins this one!
Real life example; here is a dish of 6 cooked egg whites (180 calories) that I just finished eating vs a small cinnamon roll (160 calories) I did not eat. Which one do you think will leave me less hungry?
Individual preference: another often-neglected factor in determining how satisfying and satiating a certain food is depends on individual preference. You may not like the taste of lettuce, but I may. You may despise the thought of cranberries, but having a handful of cranberries will keep me content!
Complex carbs: complex carbs will USUALLY be more satiating than simple carbs. I mean, would you rather have a bowl of whole wheat pasta (~180 calories) or 3 tablespoons of honey (also 180 calories)? Considering individual preference, of course. But yes, whole wheat pasta will break down slower in the stomach (low glycemic) and thus keep you fuller for longer.
Fiber: remember when we spoke about dietary fiber? Well, as you learned, dietary fiber is mostly indigestible and slows down the digestion process of other foods, thus the food stay longer in the digestive system which in turn keep you feeling full.
Protein: protein is known to be the most satiating macronutrient, thus, the higher the protein content in a given food, the more satiating it will be. The same example of the cooked egg whites above applies.
Water content: how much water a food has will contribute to its total volume. Celery is a perfect example. Celery is mainly water in disguise, thus it has more volume than let’s say hmmm…sugar!
Individual physiological differences: once again, our bodies are different, and they all process foods differently (not completely but you get the idea) and thus they crave different foods. For instance, some people are carb sensitive and will favor having some carbs over a high fat snack. To those individuals, carbs are more satiating!
Mechanical digestion: try eating a cup of cottage cheese and a cup of blueberries RAW, then take the same amount of both ingredients and puree them in a blender to make a smoothie, tell me which one made you feel fuller. I guarantee that eating both cottage cheese and blueberries raw left you fuller than having the smoothie, thus the process of mechanical digestion enhances satiety. This is also affected by the cooking method. This leads me to the next point.
Texture: the texture of food affects the satiation effect of it as well. For example, try having a cup of Greek yogurt and a cup of cottage cheese on different occasions, cottage cheese will most likely keep you more satiated due to having dewy pieces in it while the Greek yogurt is smooth.
Nutrient density: There is very strong evidence that your body forces you to eat by stimulating hunger because you are deficient in certain micronutrients! This even makes sense from a survival mechanism’s perspective, your body senses that you are deficient in a specific mineral or vitamin that is crucial to your health, guess what it does? It forces you to eat more food in an attempt to achieve the certain threshold of that vitamin that your body needs.
Satiety index and an optimal diet plan
You can mostly eat whatever you want and still lose weight, given that you are eating at a caloric deficit, of course. However, an optimal diet plan will also take the satiety index into account when it’s designed. The reasons satiety index plays a major role in designing an optimal and successful diet plan are:
- Satiety index will build your diet plan around foods that will keep you full.
- Foods with a high satiety index will save you from hunger attacks, especially when losing weight gets harder.
- The more weight you lose, the more your body will try to fight back and force you to eat, thus, staying full is crucial for achieving your goal.
- Satiety index will keep you sane by allowing you to eat different filling foods.
- From a psychological perspective, satiety index considers the differences in individual cravings and hunger tolerance. We are all different, some can put up with hunger, and some can’t due to different physiological and psychological reasons.
- The higher the satiety index of a food, the more nutrient dense it is, which will help with weight loss and overall health, of course.
You can decide to eat chocolate all you want and still lose weight if you are at a caloric deficit, however, besides that this is not a good idea, you will experience hunger every so often that it will be inevitable for you not to snap and binge eat everything in sight. However, an intelligently designed diet plan will take satiety index into account.
Fullness Factor is Bullshit!
If you have been reading about satiety index, I am sure you have across the fullness factor that was “developed” by ND. I have something to tell you, it’s complete crap! Fullness factor is crap because all it did was confirm the findings of Holt’s study, but instead of expressing the data as percentages, they expressed it as numbers on a scale from 1-5, how brilliant! One might point out their following formula:
“FF=MAX(0.5, MIN(5.0, 41.7/CAL^0.7 + 0.05*PR + 6.17E-4*DF^3 – 7.25E-6*TF^3 + 0.617))”
Now, if you have been reading along, while this formula takes into account the energy, protein, dietary fiber and fat contents, this equation is mere speculation! The formula does NOT take into account the caloric density of different foods, individual preferences, volume, glycemic index effect (fiber is close, though), water content…etc. Thus, the equation is incomplete. And why the heck does the equation take fat content into account anyway? Fat has the highest energy content per gram compared to any of the other macronutrients, yes fat is delicious, but it is not filling whatsoever, unless you have a good amount of it, which will be accompanied by a considerable number of calories as well!
Prediction of high satiating foods
Since this is a huge, yet fundamental topic, I will be working on creating a list of the most satiating foods that I have come across from personal experience, research studies and foods that take the aforementioned factors into account. Stay tuned! For now, just follow the guidelines above. A simple list of good satiating foods is:
- Boiled potatoes
- Boiled/baked yams.
- Rye bread.
- Whole grains.
Update: I have created a list of the most satiating foods here, be sure to check it out. The list will be updated regularly.
How to use satiety index when designing your diet plan?
- Design your diet plan around real food and not processed crap because that real food’s caloric density will be less than that of processed foods.
- Real food will also have more nutrients. A micronutrient deficiency might lead your body to stimulate hunger, however, if you eat more real food, you will most likely acquire your daily requirements of vitamins and minerals.
- Pick foods that are voluminous. Example, lettuce, spinach, chicken breast, honeydew…etc. The sky is the limit here.
- Pick foods that are high in fiber.
- Include foods that protein rich. Protein is satiating, eat more of it.
- Eat more hard textured foods. Raw foods involve more mechanical digestion (chewing, grinding…etc) which will help aid in making you feel satiated.
- Include foods that YOU like. Remember that satiation has subjective factors as well. If you want to eat a bit of junk every now and then to stay happy and keep yourself sane, that’s fine, as long as the MAJORITY of your diet consists of REAL food.
Take home message
When you or someone else designs a diet plan, make sure they consider satiety index while designing it. Losing weight and eating can go hand in hand, you do not need to suffer to lose weight. Food is one of life’s best pleasures, and unless you are getting ready for a competition, runway show or bodybuilding show, you won’t need to go on an extreme diet. Have fun, use your common sense and follow the guidelines above and stay consistent.
PS: Fat is not the enemy, I just wanted to point that out before someone misunderstands me. So, eat your fats too!
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Holt SH, M. J. (1995, September). A satiety index of common foods. Retrieved from PubMed: https://www.ncbi.nlm.nih.gov/pubmed/7498104
J O Hill, C. M. (1995, November). Physical activity and energy requirements. Retrieved from The American Journal of Clinical Nutrition®: http://ajcn.nutrition.org/content/62/5/1059S
Joel Fuhrman, B. S. (2010, November 7). Changing perceptions of hunger on a high nutrient density diet. Retrieved from US National Library of Medicine: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2988700/
Singh, M. (2014, Sep). Mood, food, and obesity. Retrieved from US National Library of Medicine : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4150387/
Thomas L. Halton, F. B. (2004). The Effects of High Protein Diets on Thermogenesis, Satiety and Weight Loss: A Critical Review. Retrieved from University of Colorado: http://www.colorado.edu/intphys/Class/IPHY3700_Greene/pdfs/atkins/haltonProtein2004.pdf