How Dinner Plate Size Affects Your Weight
Three words define American food culture: “Super Size Me.”
Hamburgers have expanded by 23 percent. A plate of Mexican food is 27 percent bigger. Soft drinks have increased in size by 52 percent. Snacks—potato chips, pretzels, crackers—are 60 percent larger.
Why have portion sizes gotten so big? Were they a response to our growing hunger?
The answer is so surprising, so counterintuitive, that scientists studied it for years before they reached a consensus. Their conclusion? Portion sizes haven’t increased as a response to growing hunger. Our hunger has increased as a response to bigger portions.
The evidence for it is so pronounced, so extensive and substantive, food scientists have a name for it: The Portion Size Effect. Basically, the more food you’re served the more you’ll eat.
A meta-analysis of sixty-five studies involving 109 separate observations showed that doubling the amount of a portion results in approximately a 35% increase in the amount of food eaten.
Bigger Portions Means More Eating
Scientists can come to no other conclusion: Bigger portions incentivize us to eat more. And as you're about to find out, plate sizes have dramatically increased. This means we're serving ourselves much bigger portions than we ever have.
In a classic, representative study of The Portion Size Effect, participants were served a deli-style sandwich, of which they could eat as much as they wanted. The first week they were served 6” sandwiches. Each subsequent week they were served larger sandwiches (8”, 10” and 12”) and asked to report satiety levels.
Guess what happened? The bigger the sandwich the more participants ate. Now that’s surprising enough but what came next was shocking and much harder to explain. You would expect people eating larger portions to report more satiety. They didn’t.
Despite the substantially greater intake of larger sandwiches, participants reported no more satiety at the end of the meal than did participants eating the smaller sandwiches. Isn’t that like saying you didn’t feel any fuller on Thanksgiving than a typical weeknight dinner?
How is this possible? How could you feel no fuller eating a sandwich that’s twice the size of what you normally eat? Wouldn’t leptin, the satiety hormone, send urgent signals to stop eating? Wouldn’t the stomach walls, stretched beyond normal capacity, make you feel bloated and uncomfortable?
Brain Uses Portion Size To Determine Hunger
From a physiological standpoint, this makes no sense. But ask a neuroscientist and they’ll tell you it makes perfect sense. It’s the brain that ultimately determines our hunger and satiety, not the stomach. In fact, the brain often overrides stomach sensors if it believes it has a more reliable source to construct hunger and satiety.
Remember how amnesiacs didn’t feel full after they’d eaten several lunches? The brain short-circuited physiological sensors in favor of memory. Since there weren’t any memories of eating, the brain ignored the body’s urgent signals of satiety.
It’s not memory (or the lack of it) causing The Portion Size Effect; it’s the brain’s trust in portion size as the arbiter of satiety.
As stated earlier, the brain doesn’t “know” how hungry the body is or how much we should eat. It uses an incalculable amount of data to make a prediction. We’ve already seen how much value it places on memory. What we haven’t seen is how much value it places on social norms.
Portion size communicates how much is appropriate to eat. It acts as an upper limit for intake, defining how much can be maximally eaten without being perceived as an excessive eater.
Portion size is a social construct. It’s like money—it is what it is because we’ve all agreed to it, not because it’s a manifestation of natural law. In societies where the socially-approved portion size is smaller, the brain expects satiety to come with less food. In societies where the socially-approved portion size is bigger, the brain expects satiety to come with more food.
Portions are proxies for satiety. Consequently, the brain eats to the portion.
Bigger Portions Means Bigger Bites
How does The Portion Size Effect change our eating? Researchers believe “The Bite Size Mechanism” takes over. Your brain looks at the size of the portion and automatically adjusts how much food you put on your fork. If it’s a small portion your bite size shrinks. If it’s a bigger portion the bite size increases. Basically, how much food you put in your mouth changes depending on the size of the portion.
Hence, the danger of bigger portions: You’ll use bigger bites to get at it, which increases the eating rate and the duration of the meal (larger portions take more time to eat even if your bite size is greater).
You can see the “Bite Size Mechanism” at work in non-food items like laundry detergent. For the same-sized bundle of dirty clothes, you’ll likely use less detergent if it comes in a small box and more detergent if it comes out of a big one, even though the directions on both boxes recommend using the same amount.
Why Did Portions Get Bigger?
If hunger didn’t drive the rush towards larger portions what did? The answer is self-evident when you consider who benefits from increased hunger.
Remember, portion sizes represent social norms. They’re set by cultural standards handed down over the years, usually by people and institutions expected to have knowledge about the “correct” amount to eat, such as the cook in the kitchen, the chef in a restaurant, the author with a recipe, the foodie with knowledge, the researcher in a lab and…
Big Food.
Yes, Big Food is a key player in establishing social norms in portion sizes. After all, they’re the ones packaging and marketing the amount of food we “should” be eating. It is there, in Big Food, that we can most vividly see the march towards bigger and bigger portions.
Nabisco makes double-cream Oreos. McDonald’s serves fries that have grown 254% since they opened in the 50’s. Costco stocks “value size” packages the 5th Infantry couldn’t get through. The Cheesecake Factory offers McFrankenstein creations that could put diabetics into a coma.
On and on, portions grow. The result?
We get habituated to bigger portions.
It isn’t just portions that have increased in size. Everything did—even the plates, bowls, glasses, forks, knives and spoons we use to get at the increased portion sizes.
This habituation to bigger sizes created a phenomenon researchers call “Portion Distortion,” a perception of large portions as normal. Portion Distortion, along with The Portion Size Effect create a reinforcing loop: Bigger portions create greater hunger which fuels the desire for bigger portions which generates more hunger.
Reversing Portion Distortion and The Portion Size Effect will help you lose weight. You can find easy-to-implement solutions in the online course NeuroSlim.
How Plate Size Affects Your Weight
American plates are now larger than ever, and so are American food portion sizes. Science shows that these two are closely linked. The reason plate size is so important to consider is that it affects the way we perceive the amount of food we’re eating, and thus affects our consumption.
Studies show that we’re terrible at estimating the amount of food on our plates, and we might not be aware of it.
A study investigating the change in American dinner plate sizes over the years looked at the plates on eBay that were manufactured between 1900 and 2010.
Over this period, they found that the plate sizes were increasing gradually. The smallest plate size was 9.6 inches made in around 1900. The largest plate size was 11.8 inches, made in around 2010.
This means that the plates increased in size by approximately 23% from 1900 to 2010 [1]. This is important because a larger plate size has been linked to a larger serving size and higher food intake.
The same study examined this effect by asking 225 college students to serve the same amount of soup in a bowl. There were in total 7 bowls of different sizes, and they had to estimate the amount of soup they needed to serve in the bowl that they were assigned.
The researchers found that the participants who had a smaller bowl served less soup, and the participants who had a larger bowl served more. This is referred to as the Delboeuf illusion. People underestimate the amount of food on a big plate, and they tend to overserve and overconsume [1].
A study was conducted on 281 adults in the U.S. They were asked to draw their dinner on 2 paper plates of different sizes. One plate measured 9 inches and the other 11 inches, approximately.
Study participants drew 24% more food on the bigger plates than the smaller ones, and men had a more pronounced effect than women [2]. They believed the plates had the same amount of food they visualized. They didn’t realize that the change in plate size affected their perception of how much food they drew.
Another study looked at Chinese buffet diners and compared their plate sizes and customer consumption behaviors, and found that customers served 52% and ate 45% more food in diners that have large plates compared to those that have small plates. They also wasted 135% more food.
The authors explain that the size of a plate serves as a measuring tool for the brain to know how much food is appropriate to eat. It creates an illusion that the food is a different size than it actually is, by comparing it to the size of the plate. This affects not only serving size, but also consumption and the amount of food waste [3].
The same results were observed in a study on plates and wine glasses. A total of 140 participants were offered plates of different sizes and shapes in the first experiment, and wine glasses and bottles of different sizes in the second experiment.
In average, participants served around 61% more food in large plates compared to small plates, and around 27% more wine in large glasses than small glasses [4].
In fact, even the width and color of the plate rim were proven to affect food portion estimation by making the center of the plate appear larger or smaller.
In a study, participants were shown images of plates of the same size that have rims of different widths and colors, and were asked to choose the plate that had more food on it.
The researchers found that the area of the food on plates with a wider rim was overestimated by 10% compared to the ones with a smaller rim, and the area of the food on plates with a colored rim was overestimated by 3% compared to plates with colorless rims. This study proves that the overestimation is due to a visual illusion. Plate size, or perceived plate size can affect the perception of portion size [5].
Given the results of these studies and the significant increase in plate sizes in the U.S, it is not a surprise that portion sizes continue to increase and exceed federal standards in multiple food categories [6][7].
It may be useful for people with weight loss or maintenance goals to get rid of large plates and only use small and medium sized plates. It’s a small change but it can have a significant effect in reducing food intake.
References:
1. Van Ittersum, K., & Wansink, B. (2012). Plate Size and Color Suggestibility: The Delboeuf Illusion’s Bias on Serving and Eating Behavior. Journal of Consumer Research, 39(2), 215–228. https://doi.org/10.1086/662615
Quote: The average size of a sample of dinner plates increased increased almost 23% from 9.6 inches to 11.8 inches, since 1900.
2. Sharp, D., Sobal, J., & Wethington, E. (2019). Do Adults Draw Differently-Sized Meals on Larger or Smaller Plates? Examining Plate Size in a Community Sample. Food quality and preference, 74, 72–77. https://doi.org/10.1016/j.foodqual.2019.01.012
Quote: Overall, these findings support the concept that adult participants' estimates of dinner meal size may be shaped by plate size.
3. Wansink, B., & van Ittersum, K. (2013). Portion size me: plate-size induced consumption norms and win-win solutions for reducing food intake and waste. Journal of experimental psychology. Applied, 19(4), 320–332. https://doi.org/10.1037/a0035053
Quote: We contend that dinnerware provides a visual anchor of an appropriate fill-level, which in turn, serves as a consumption norm (Study 1). The trouble with these dinnerware-suggested consumption norms is that they vary directly with dinnerware size--Study 2 shows Chinese buffet diners with large plates served 52% more, ate 45% more, and wasted 135% more food than those with smaller plates.
4. Clarke, N., Pechey, E., Pechey, R., Ventsel, M., Mantzari, E., De-Loyde, K., Pilling, M. A., Morris, R. W., Marteau, T. M., & Hollands, G. J. (2021). Size and shape of plates and size of wine glasses and bottles: impact on self-serving of food and alcohol. BMC psychology, 9(1), 163. https://doi.org/10.1186/s40359-021-00645-z
Quote: Smaller tableware (i.e. plates and wine glasses) decreases the amount of food and wine self-served in an initial serving.
5. McClain, A. D., van den Bos, W., Matheson, D., Desai, M., McClure, S. M., & Robinson, T. N. (2014). Visual illusions and plate design: the effects of plate rim widths and rim coloring on perceived food portion size. International journal of obesity (2005), 38(5), 657–662. https://doi.org/10.1038/ijo.2013.169
Quote: The Delboeuf illusion applies to food on a plate. Participants overestimated food portion size on plates with wider and colored rims.
6. Nielsen, S. J., & Popkin, B. M. (2003). Patterns and trends in food portion sizes, 1977-1998. JAMA, 289(4), 450–453. https://doi.org/10.1001/jama.289.4.450
Quote: Between 1977 and 1996, both inside and outside the home, portion sizes increased for salty snacks, desserts, soft drinks, fruit drinks, french fries, hamburgers, cheeseburgers, and Mexican food. Pizza portions in general decreased during this period. The size of the increases are substantial.
7. Young, L. R., & Nestle, M. (2002). The contribution of expanding portion sizes to the US obesity epidemic. American journal of public health, 92(2), 246–249. https://doi.org/10.2105/ajph.92.2.246
Quote: Marketplace food portions have increased in size and now exceed federal standards. Portion sizes began to grow in the 1970s, rose sharply in the 1980s, and have continued in parallel with increasing body weights.
The largest excess over USDA standards (700%) occurred in the cookie category, but cooked pasta, muffins, steaks, and bagels exceeded USDA standards by 480%, 333%, 224%, and 195%, respectively. Our data indicate that the sizes of current marketplace foods almost universally exceed the sizes of those offered in the past.