Big bowls may lead to big bellies, according to a new review designed to explain why people overeat. After examining dozens of studies, researchers from the University of Cambridge found tableware and package size can play a role in how much food a person consumes. Their findings, published in the Cochrane Database of Systematic Reviews, reveal how this influence affects everybody, regardless of their weight, gender, or age.

“People see someone who’s overweight and may presume they have no control over what they do, and [that] they just overeat,” the study’s co-author Dr. Gareth Hollands, a senior researcher of health psychology at the University of Cambridge School of Clinical Medicine, told Medical Daily. “It might be nice to think it’s all decided by people’s conscious choices to go ahead and do something, but we’ve actually seen all these environmental factors and external cues, including package and plate sizes that are extremely important to shaping our eating behavior.”

Hollands and his colleagues looked at results from 61 studies, which included 6,711 participants who ate in a variety of different real world environments. They found that reducing the size of portions, packages, and tableware in a person’s everyday diet could cut 22 to 29 percent of their daily calories — an average of 527 calories each day. “It was surprising how consistent the effect seemed to be considering packaging and tableware had a substantially similar effect on children and adults, whether they were male or female, overweight, or had different levels of self-control,” Hollands said. “The indications so far point that this has a robust effect across the population.”

Size isn’t the only factor that affects how much a person consumes; price does, too. And although the researchers analyzed studies that focused on how much a person ate from their plate rather than how much they were willing to spend in relation to their eating habits, the findings could suggest pricing plays a part. Buying food in bulk costs less and is financially more sensible than opting for smaller portions, even though it comes with caloric consequences. One way to decrease the likelihood of overeating, the researchers said, could be to limit the savings consumers get from buying in bulk.

When burritos become as big as your head, they set a consumer up to believe they’re getting a better deal, according to Cornell Food Scientist Brian Wansink’s recent book Slim by Design. But the more-calories-per-dollar method doesn’t benefit the customer’s health or the food industry’s bottom line. Wansink referred to a Chinese buffet owner who switched out his 11-inch plates for 9-inch plates and found customers took less food, wasted less, ate less, and cost the restaurant less.

Little tricks like this won’t deter customers, either. In one study, Wansink and his colleagues found that when they reduced the size of plates, people rated the food as a better value even though there was 15 percent less food on their plate. It just appeared there was more food, which in turn left customers more satisfied with their meals, leading Wansink and his team to say more food doesn’t necessarily lead a customer to believe they’ve gotten a better deal.

"At the moment, it is all too easy — and often better value for money — for us to eat or drink too much," said the study’s co-author Dr. Ian Shemilt, a senior behavior and health researcher at the University of Cambridge, in a press release. "The evidence is compelling. Reducing the size, availability, and appeal of large servings can make a difference to the amounts people eat and drink. We hope that our findings will provide fresh impetus for discussions on how this can be achieved in a range of public sector and commercial settings."

Source: Hollands GJ, Schemilt I, Marteau TM, et al. Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Cochrane Database of Systematic Reviews. 2015.

Wansink B. Environmental Factors That Increase the Food Intake and Consumption Volume of Unknowing Consumers. Annual Review of Nutrition. 2004.