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Bite-sized portions can backfire on your diet

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Smaller forks may actually make you eat more when dining out, counterintuitive new research shows.

Using a smaller fork at a restaurant may encourage you to eat a larger portion than a larger fork, a study shows. You might think a smaller utensil would reduce consumption, but it actually increased it when dining out.

This new research focused on bite size -- or the amount of food in each mouthful -- which can vary both within a meal and from person to person. Since it's impolite (and disgusting) to peek into someone's mouth while they're chewing, researchers used fork size as a measure of bite size.

The study, published online in the Journal of Consumer Research, evaluated how fork size influenced the amount of food eaten by diners in an Italian restaurant. During two lunches and two dinners, researchers compared how much food was consumed by those given either a large fork, which held 20 percent more food than a regular one, or a small fork, which held 20 percent less.

They weighed the contents of each plate before and after it was served, and also controlled for other factors that can influence restaurant consumption, such as price, whether it was lunch or dinner, and if alcohol or an appetizer was had with the meal.

Diners left more food on the plate when using a large fork rather than a small one -- a pattern opposite what studies have shown for portion size where larger servings or food packages encourage more eating.

"The finding with a large fork is counterintuitive," says Arul Mishra, an associate professor of marketing at the University of Utah in Salt Lake City, and the study's lead author.

Here's another oddity: Scientists ran a similar study asking 81 people to eat a preweighed bowl of pasta salad, but instead of dining out, the participants ate in a lab setting. Volunteers used the same small or large forks from the restaurant study and were told to eat as much as they wanted.

This time, though, participants who ate with a large fork consumed more pasta salad than those using a smaller one -- the reverse of what was seen in a restaurant and similar to results from portion size studies.

Why the difference?

Mishra suspects the lab participants probably did not have a well-defined hunger goal and did not pay money to consume a food of their choice. So they had different motivations than people dining out, who invest more time, effort and money in their meal.

But in a restaurant, fork size only made a difference for larger portions. Faced with a big plate of food, "people don't visually feel that they are making progress toward satiating their hunger goal with a small fork," suggests Mishra, so they consume more.

She says it's unclear how these results apply to home-cooked meals since this wasn't studied. Even so, her advice is to decide for yourself whether you've had enough to eat by tuning into those feeling-full body signals rather than to your brain. External cues -- fork size, plate size, portion size -- can be misleading and lead to overdoing it.