Here’s a well-known weight-loss tip: use a smaller plate, and you’ll be satisfied with a smaller portion. The tip works — provided you’re not genuinely very hungry — because a large part of our satisfaction at the end of a meal is determined by expectations about what a decent meal looks like. If we feel like we’ve eaten a proper dinner, we’re not likely to eat another one an hour later.
If the sight of our meals matters, then how about the sight of each bite? Business-school researchers at the University of Utah, Salt Lake City, conducted a clever experiment — published recently [PDF] in the Journal of Consumer Research — to find out.
The study authors enlisted help from a local Italian restaurant. Over the course of two days — serving two lunches and two dinners — the researchers randomly selected tables to receive either unusually large forks (20% larger than the restaurant’s normal fork) or unusually small forks (20% smaller than normal). They then weighed each plate of food before it went out to a customer and once again when it came back, in order to calculate how much each person had eaten.
Overall, the results showed, the customers given bigger forks ate less, leaving more on their plates at the end of each meal.
That left the study authors trying to explain why people might eat more when they’re given bigger portions, but less when they’re given bigger forks? The study authors suggest that both phenomena can be explained by the same logic. In their paper they write:
[D]iners focus on the visual cue of whether they are making any dent in the amount of food on their plates [...]. The smaller fork (compared to the larger fork) appears to provide less satisfactory goal progress; that is, diners feel they are not making much of a dent in consuming their food and, hence, satisfying their hunger. This, in turn, focuses diners to put in more effort (e.g., more forkfuls) toward satiating their hunger. As a result, diners with smaller forks consume more food than those using larger forks.
By this same logic, if the food portion is very large to begin with, diners will eat more of it because they don’t notice themselves making a dent in the meal until a lot has been consumed.
The argument also suggests an interplay between bite size and portion size. In the experiment, restaurant-goers who received both small forks and large portions ate disproportionately more than either one of those factors alone would predict.
Importantly, however, the bigger fork may encourage people to eat less only when their goal is to eat a full meal and satisfy their hunger — precisely the goal of most restaurant-goers. The study authors also tested the effect of fork size on food consumption among people were not necessarily hungry, but who instead were merely snacking.
They gave university students some pasta salad and the same large forks and small forks that were used in the restaurant experiment. They found that, when people were presented with food outside of a mealtime, larger forks led people to consume more. The students were, perhaps, less concerned about making a dent in any food they were given, so that they simply took a few bites out of habit. In that scenario, the authors write, people may “become more willing to anchor on the fork size as the appropriate bite size.”