How To Eat Less

Portion Size Influences Calorie Consumption

Is it a shock to learn that the portion sizes of what we now call “kid’s meals” from fast food restaurants where once considered adult-sized portions?

When McDonald’s opened inn 1955, there was only one size of French fries on offer—a serving that equaled about 2.4 ounces, about .2 ounces less than what we give small children in their kid’s meals today.

A large order of fries serves up nearly 6 ounces, more than double than the original 1955 serving size. 

In the decades since McDonald’s and Burger King became central to America’s dietary identity, portions have “supersized” to a degree that some argue Americans have lost all perspective on what constitutes reasonable or moderate portions.

It is no coincidence, many claim, that rates of obesity have skyrocketed in line with the growth of oversized portions in most homes and restaurants.

According to the Centers for Disease Control and Prevention, our average restaurant meal size is four times larger than when McDonald’s entered the fray. 

Some studies says that 96% of these meals exceed our dietary requirements for sodium and fat.

But just because correlation strongly implies causation in this situation doesn’t mean that it is so.

Why You Should Eat In Moderation

Researchers, needed hard proof to see how growth in portion sizes influences calories consumed.

Food marketers, facing social criticism for their role in America’s obesity epidemic, decided to test the claim that larger portions induce overeating.

They found, to their dismay, that critics were right. Larger portions resulted in greater consumption. 

In “Sizing up the Effect of Portion Size on Consumption: A Meta-Analytic Review,” published in the Journal of Marketing, found that larger portion sizes did indeed “encourage greater consumption, which can cause excessive consumption and obesity.

The researchers focused on two questions: “1) How much effect does portion size have on consumption? And 2) Are there limits to this effect?”

Their meta-analysis revealed consistent results: “for a doubling of portion size, consumption increased by 35% on average.” On average.

That means some participants increased their consumption by as much as 60% while others perhaps by only 10%. Either way, the result was clear. People eat more when bigger portions are placed in front of them. 

Interestingly, the portion-size effect is limited: “An extended analysis shows that the effect of portion size is curvilinear: as portions become increasingly larger, the effect diminishes.”

The study also pointed out while the effect of increasing serving sizes on amounts eaten is “robust,” the “analysis shows that it is weaker among children, women, and overweight individuals, as well as for non-snack food items.”

How To Eat In Moderation And Lose Weight

While the confirmation that increasing portions sizes do result in increased consumption, food marketers are unlikely to change their offerings as long as they continue to provide a profitable stream of revenue.

As a result, it is up to the individual consumer to be aware of the correlation and determine how to best respond to it.

In The American Journal of Clinical Nutrition, researchers confirmed that, “Portion size of food affects energy intake in normal-weight and overweight men and women.”

But rather than a meta-analysis of existing studies, they designed their own with “51 normal-weight and overweight men and women aged 21-30 years.

To no one’s surprise, “subjects in both groups consumed significantly greater amounts of the lunch entrée as portion size increased…subjects consumed 30% more food when presented with the largest portion than when presented with the smallest portion.”

Subjects self-reported rates and hunger and fullness after meals, which “did not vary,” even when more food was presented. This “suggests that portion size influences the development of hunger and satiety.

Researchers conjecture that one possible explanation is that “people have the expectation that the amount of food served to them is appropriate.” They also point out that “most people are unaware of what constitutes an appropriate portion and…do not notice variations in portion size.”

Since portion control is a “modifiable environmental factor,” educating people about appropriate portions is recommended. 

Worryingly, the research journal, Obesity, reports in the article, “The Effect of Large Portion Sizes on Intake is Sustained for 11 Days,” that said overeating continues unabated (in this study for 11 days) as long as portion sizes are increased.

In other words, there appears to be no internal adjustment when consistently presented with supersized portions. People will continue to overeat as long as oversized portions are placed before them. 

In the Obesity study, the “50% increase in portion sizes resulted in a mean increase in intake of 423 kcal per day over the 11 days of the study, for an average cumulative increase of 4,636 kcal.”

The idea that the biological system would automatically regulate after a period of time is not supported. “The increased consumption associated with large portions was associated with decreased hunger and increased satiety, but these sensations were not sufficient to adjust intake.”

In other words, it promotes overeating and “dysregulation of energy intake that may contribute to the development of obesity.”

How We Compare To Other Cultures

Let’s take the French as an example. Their refrigerators are small, food storage is uncommon (due to small pantries) and their portion sizes are considerably smaller.

One study compared portions between Paris and Philadelphia restaurants and found that French portions were, on average, 25% smaller.

Another study compared the popular U.S. cookbook, Joy of Cooking with a similar French cookbook. Portion sizes in the American recipes were 25 percent larger. In meat dishes, they were 53 percent larger.

Neuroscientists believe that the brain, when it can’t get a good read on the stomach’s fullness, will accept portion size as a proxy for satiety. 

The brain knows the quantity in a portion is established by social norms of what is typical or acceptable. Therefore, the brain believes it can’t reach satiety until the portion is finished.

Now, you don’t have to drop a bag of marbles to see how this floor is sloping. If your portions are big (and they always are in the West) you’re not going to feel satisfied until the last bite, regardless of how full you really are.

This explains why Epicurean societies feel just as full eating a smaller portion as Viscerals do eating larger portions—because the brain eats to the socially normative portion.

How To Eat Less Food

Now that we know how we got here, how do we get out? The same way we came in—through habituation. We didn’t go from standard portion sizes to Godzilla servings all at once; we can’t go back the same way, either.

Most people fail at reducing the size of their portions because they violate habituation’s golden rule: Thou shalt not awaken the startle response.

Think about the anxiety, disappointment and anger you experienced the last time you got served a drastically-reduced portion. It felt like somebody threw you into a cauldron of boiling water, no?

Like any good frog, you jumped out.

The decreased portion size represented a threat. Your sensors (anxiety, the threat of deprivation) activated the regulatory powers of homeostasis which then restored equilibrium by making you even hungrier so you’d search for more food.

Remember, it’s not the size of the portion that creates our dissatisfaction; it’s the size of the decrease.

Surprisingly, the worst offenders, the people who constantly violate the rules of habituation, are the very people who should know better—diet and nutrition experts.

They’re always urging us to eat smaller portion sizes, regardless of what we’ve habituated to. Used to drinking 6 cans of soda?

Dietitians will tell you to quit and drink water. Used to eating 12 oz of steak? They’ll tell you to eat 4 oz instead.

Have you ever seen the difference between a 4 oz and 12 oz piece of steak? Your startle response would go off like a howler monkey screaming against the window of a NASA rocket at liftoff.

Ignore the dieting experts. Don’t ever make that kind of reduction all at once. And their recommendation to measure your food?

It’s fine if you want to get a better understanding of what a standard portion looks like, but never measure to find out how much you should eat. Measure to understand how much you’re currently eating so you can start the process of systematic discontinuation.

The key to downsizing portions isn’t to go from large to small. It isn’t even to go from large to medium. It’s to go from large to a hair smaller than large. And from there to a hair smaller than that.

The body responds to “cutting back drastically” like a jet that makes a sudden 90 degree turn at 600 MPH.

The people in the cabin scream, panic, cry, and pray as everything that isn’t bolted down flies across the seats (including the passengers).

Even after the plane straightens out, panic remains. Compare that to the jet turning one degree at a time. Yes, it takes a lot longer, but it’ll get there on time and the passengers will be safer, calmer, and happier with the results.

Academic Studies Informing This Article On Eating In Moderation

  Zlatevska, N., Dubelaar, C., & Holden, S. S. (2014). Sizing up the Effect of Portion Size on Consumption: A Meta-Analytic Review. Journal of Marketing, 78(3), 140–154. https://doi.org/10.1509/jm.12.0303

Quote: A meta-analytic review reveals that, for a doubling of portion size, consumption increases by 35% on average. However, the effect has limits. An extended analysis shows that the effect of portion size is curvilinear: as portions become increasingly larger, the effect diminishes. In addition, although the portion-size effect is widespread and robust across a range of individual and environmental factors, the analysis shows that it is weaker among children, women, and overweight individuals, as well as for nonsnack food items and in contexts in which more attention is given to the food being eaten.

Rolls, B. J., Morris, E. L., & Roe, L. S. (2002). Portion size of food affects energy intake in normal-weight and overweight men and women. The American journal of clinical nutrition, 76(6), 1207-1213. https://doi.org/10.1093/ajcn/76.6.1207

Quote: Larger portions led to greater energy intake regardless of serving method and subject characteristics. .

Rolls, B.J., Roe, L.S. & Meengs, J.S. (2007), The Effect of Large Portion Sizes on Energy Intake Is Sustained for 11 Days. Obesity, 15: 1535-1543. https://doi.org/10.1038/oby.2007.182

Quote: These results strengthen the evidence suggesting that increased portions contribute to the overconsumption of energy and to excess body weight.

Rolls, B. J., Roe, L. S., Meengs, J. S., & Wall, D. E. (2004). Increasing the portion size of a sandwich increases energy intake. Journal of the American Dietetic Association, 104(3), 367–372. https://doi.org/10.1016/j.jada.2003.12.013

Quote: Individuals ate lunch in the lab once a week for 4 weeks. Each week, they were served one of four sizes of a deli-style sandwich (6, 8, 10, or 12 inches), of which they could eat as much as they wanted. These results suggest that increasing the portion size of a food served as a discrete unit leads to increased energy intake at a single meal without differentially influencing ratings of hunger and satiety.

Hollands, G. J., Shemilt, I., Marteau, T. M., Jebb, S. A., Lewis, H. B., Wei, Y., ... & Ogilvie, D. (2015). Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Cochrane database of systematic reviews, (9). https://doi.org/10.1002/14651858.CD011045.pub2

Quote: This review found that people consistently consume more food and drink when offered larger‐sized portions, packages or tableware than when offered smaller‐sized versions.

Rolls, B. J., Morris, E. L., & Roe, L. S. (2002). Portion size of food affects energy intake in normal-weight and overweight men and women. The American journal of clinical nutrition, 76(6), 1207-1213. https://doi.org/10.1093/ajcn/76.6.1207

Quote: Portion size significantly influenced energy intake at lunch (P < 0.0001). Subjects consumed 30% more energy (676 kJ) when offered the largest portion than when offered the smallest portion.

Kelly, M. T., Wallace, J. M., Robson, P. J., Rennie, K. L., Welch, R. W., Hannon-Fletcher, M. P., ... & Livingstone, M. B. E. (2009). Increased portion size leads to a sustained increase in energy intake over 4 d in normal-weight and overweight men and women. British journal of nutrition, 102(3), 470-477. https://doi.org/10.1017/S0007114508201960

Quote: The present study clearly demonstrates that the availability and consumption of large food portions led to significant and sustained increases in EI over a 4 d period.

Rolls, B. J., Roe, L. S., & Meengs, J. S. (2007). The effect of large portion sizes on energy intake is sustained for 11 days. Obesity, 15(6), 1535-1543. https://doi.org/10.1038/oby.2007.182

Quote: These results strengthen the evidence suggesting that increased portions contribute to the overconsumption of energy and to excess body weight.

Rolls, B. J., Roe, L. S., & Meengs, J. S. (2006). Larger portion sizes lead to a sustained increase in energy intake over 2 days. Journal of the American Dietetic Association, 106(4), 543–549. https://doi.org/10.1016/j.jada.2006.01.014

Quote: Increasing the portion size of all foods resulted in a significant increase in energy intake that was sustained over 2 days. These data support suggestions that large portions are associated with excess energy intake that could contribute to increased body weight.