Adults consume more food when it comes in bigger packages or is served on larger plates, a review of past research has found.
The study team analyzed 58 studies with a combined 6,600 participants that examined how the size of things like cereal bowls and snack bags influences the number of calories people take in.
Combined, these brief experiments suggest that smaller containers, dishes and cutlery might help adults consume up to 16 percent fewer calories in the U.K. and 29 percent less in the U.S.
"It provides the most conclusive evidence to date that people consistently consume more food and drink when offered larger-sized portions, packages, or tableware than when offered smaller-sized versions," said lead study author Dr. Gareth Hollands, a behavioral health researcher at the University of Cambridge in the U.K.
The results, published in the Cochrane Database of Systematic Reviews, highlight the important role of environmental influences on food consumption and suggest that actions to limit exposure to larger serving sizes may be effective tools for getting people eat less, Hollands said by email.
Globally, 1.9 billion adults are overweight or obese, according to the World Health Organization. Obesity increases the risk of heart disease, diabetes, joint disorders and certain cancers.
The effect of smaller sizes for dishes and packages didn't vary by gender and was similar for normal-weight, overweight and obese people, the researchers found. Only children appeared unaffected by size when deciding how much food or drink to consume.
Most of the studies reviewed didn't follow people for long periods and researchers lacked data to assess whether sustained changes in container and plate sizes over time might contribute to weight loss or maintaining a healthy weight, the authors acknowledge. They also note that they lacked data on the impact of bottle, can or glass size on alcohol consumption.
Still, when it comes to plate size, reducing the diameter by even an inch or two can make a difference in calorie consumption, said Dr. David Sharp, a nutrition researcher at Kent State University School of Health Sciences in Ohio.
Ideally, adults should use 9-inch or 10-inch plates, and children should have 7.5-inch plates, Sharp, who wasn't involved in the study, said by email. But this isn't an easy message to convey in a culture with a "supersize" mentality, he said.
"Hunters try to kill the deer with the largest antlers, fishermen tell stories of their biggest catch, and we sensationalize even the act of dieting by hosting reality TV shows such as The Biggest Loser," Sharp said. "When we are bombarded with the appeal of getting things bigger or larger, it creates a bit of dissonance that the message for our most intimate choices such as our meals, our plates and our bodies runs opposite to our culture of plenty when considering long-term health and wellness."
While plate size may matter, downsizing dishes alone may not be enough to help people lose weight, sad Dr. Donald Hensrud, medical director of the Mayo Clinic Healthy Living Program in Rochester, Minnesota.
"The obesity epidemic is a result of a number of different and complex influences," Hensrud, who wasn't involved in the study, said by email. "Recommending smaller plates is just one piece of a very large puzzle."