SAN DIEGO, California (WPVI) -- You've probably heard the advice to eat slowly if you want to eat less, and weigh less.
Now, the first scientific study to test the principle shows it works - at least in school children.
Researchers at the University of California-San Diego Jacobs School of Engineering put it to the test with 54 healthy children in Durango, Mexico.
And their findings were published in the journal "Pediatric Obesity."
The children ranged in age from 6 to 17 years (1st through 12th graders).
The 54 students were divided into two groups - one ate at regular speed, while the other was told to chew each bite for 30 seconds.
And they timed themselves, too, with a 30-second hourglass.
The children were instructed each time they took a bite, not to take another one until the hourglass was empty.
The students were not told it was a weight study. Instead, they were told it was called "Good Manners for a Healthy Future."
The results were striking.
After six months, researchers say the weight of the students in the slower eating group decreased anywhere from 2 to 5.7 percent.
And after one year, their weight was 3.4 to 4.8 percent lower.
The bioengineers say the weight in the control group increased from 4.4. to 5.8 percent. The slow eaters lost up to 6 percent of their weight.
After one year, the weight of the control group increased by 6.5 to 8.2 percent.
UC-San Diego says the results were so promising the Mexican states of Michoacan, Yucatn and Veracruz have invited the research team to bring the study's methods into their schools.
Slowing down the pace gives the brain time to realize you're not hungry anymore, so it is easier to stop, experts say.
And this tactic can be done longterm. You don't even have to change what you eat.
The bioengineers plan to do more studies with larger groups of children both in Mexico and southern California, targeting the area's large Hispanic population, which has a growing rate of overweight people.
An accompanying video is at: Slow-eating study.
Slow chewing may head off excessive weight gain in kids