KANSAS CITY, MO. — Recent research from the University of Missouri-Kansas City suggests smiling may make people appear younger and thinner.

When you smile, other people tend to see you as younger than if you are staring back with a neutral expression or frown. If you frown, you look heavier, according to two pieces of research from the University of Missouri-Kansas City’s psychology department and the lab of professor Seung-Lark Lim.

The research, which was published in the March 30 edition of the journal PLOS ONE, was led by 25-year-old Norah Hass, a third-year psychology doctoral student.

“The take home is interesting in that maybe having a positive expression will make you look younger,” Hass told The Kansas City Star. “We can see this very clear shift, of sad emotion versus happy emotion. Unless you’re trying to look old, I’d recommend you try not to look so sad and look happy.”

The research involved asking college students to sit in front of a computer and look at a range of images of male faces split into different age groups ranging from about 30 to 65. Some of the faces were smiling, other had neutral expressions.

The study participants were asked to judge the faces, within their age groups, as either “young” or “old.”

Hass found that, no matter the age group, happy, smiling faces were judged as “young” far more often than faces with neutral expressions. Neutral faces were seen as older in each age group than their happy counterparts.

In another recent study, UMKC undergraduate psychology student Trent D. Weston, who has since graduated, was the lead author on work published in the journal Frontiers of Psychology. Weston also asked college students to judge the weight of people based on hundreds of randomized faces that flashed on a computer screen. Some faces looked sad and other had neutral expressions.

The sad faces tended to be judged as heavier, according to the study.