Look at your plates and bowls. Have portion sizes crept up? Would smaller dishes help?
The Short Answer
Probably, though the two halves rest on different footing. That dinner plates have grown is the common account rather than a measured finding. That smaller dishes help is measured, but the effect runs through what you serve yourself, and does essentially nothing where the portion is plated for you. You serve what “looks right,” and what looks right is relative to the dish. A smaller plate is a constraint on the moment you decide how much to take.
Something to Sit With
When you serve yourself, your plates may be choosing your portions for you.
What would change if you used dishes 20% smaller?
Learn More
The expanding plate. Dinner plates are widely reported to have grown over the past few decades: a history with no source behind it, so take it as the common account rather than a measured one. What is not in doubt is the geometry, and you can check it on your own shelf: area goes up with the square of the diameter, so a 12-inch plate has close to 80% more surface than a 9-inch one (12 squared is 144, 9 squared is 81), room for that much more food without looking unusual.
If the expansion happened, it would have happened gradually, which would make it invisible: your plates look normal because they look like everyone else’s. Comparing a modern dinner plate with older china is one way to check the account for yourself.
The unit bias. Research by Geier, Rozin, and Doros identified unit bias: people treat one unit of something as the appropriate amount. And the effect survives a change of scale: offered candy with a larger spoon, people consumed substantially more. (The often-quoted detail, a single scoop of about twice the candy, is not in the paper’s published abstract.)[1] That is unit bias. One plate. One serving. One package. The brain uses unit boundaries as portion guides.
This means the plate size directly affects how much you serve yourself.[1] On this page’s reasoning, a full plate tends to feel like a complete meal whatever its size, and a sparsely filled one like deprivation, even if it held plenty of food. When you serve yourself, you may be filling the container you’ve been given more than choosing a portion.
The research evidence. A meta-analysis of 56 studies found that doubling plate size increases consumption by 41%.[1]
But the same analysis found the condition that matters, and it is the one most advice leaves out: the effect runs almost entirely through self-serving. Where the portion is plated for you and held constant, changing the plate does essentially nothing.[1] A smaller plate is not a trick that shrinks appetite: it is a constraint on the moment you decide how much to take.
The visual illusion, as usually told. The same portion is often said to look smaller on a large plate and larger on a small one, by way of a known optical illusion; whether it applies to food is not established. What the plate studies measure is the self-serving effect above.
The audit. Look at what you’re currently using:
Dinner plates: Measure them, and compare your largest against your smallest. The gap is the point, not any particular number.
Bowls: A “normal-looking” fill level in a large bowl holds more than the same fill level in a small one, and larger tableware, bowls included, raises intake.[1]
Serving dishes: Family-style meals mean serving from communal dishes, and larger serving dishes go with larger servings.[1]
The intervention. The fix is simple: use smaller dishes.
Your smaller plates for main meals, rather than the largest in the cupboard.
Smaller bowls for cereal, soup, ice cream: anything where you fill the bowl.
You don’t need new dishes. You might already own smaller plates used for salad or appetizers. Use those for dinner.
Further reading:
- Geier AB, Rozin P & Doros G, “Unit bias: A new heuristic that helps explain the effect of portion size on food intake”[2] — Psychological Science, 2006
- Holden SS, Zlatevska N & Dubelaar C, “Whether smaller plates reduce consumption depends on who’s serving and who’s looking: A meta-analysis”[3] — Journal of the Association for Consumer Research, 2016
- Robinson E et al., “What everyone else is eating: a systematic review and meta-analysis of the effect of informational eating norms on eating behavior”[4] — Journal of the Academy of Nutrition and Dietetics, 2014
Written by AI, directed and approved by me. How this is made →