Male mice that were fed yogurt on a regular basis were not just shinier, but they also exhibited more “mouse swagger” because of their bigger and heavier testicles, according to researchers replicating previous studies on the effect of yogurt on preventing age-related weight gain.

Massachusetts Institute of Technology researchers found that yogurt-eating mice had testicles that were approximately 5 percent to 15 percent heavier, inseminated partners faster and produced more offspring than those that were on a standard of junk-food diet, Scientific American reported.

Female mice on a yogurt diet also had reproductive advantages like giving birth to larger litters weaning their offspring with more success compared to control subjects.

Co-authors cancer biologist Susan Erdman and evolutionary geneticist Eric Alm, studying the effects of a probiotic diet on obesity and excess-weight related conditions, wanted to replicate a previous long-term study from Harvard School of Public Health that had suggested yogurt was better than any other food in preventing age-related weight gain.

Erdman and Alm took a group of 40 males and 40 female mice and fed them a low nutrient “junk-food” diet, or standard mouse meals, and added vanilla-flavored yogurt to half of each diet group.

“We knew there was something different in the males, but we weren’t sure what it was at first,” Erdman told ABC News on Monday. “You know when someone’s at the top of their game, how they carry themselves differently? Well, imagine that in a mouse.”

Erdman said that researchers soon noticed that yogurt-eating mice had testicles that protruded out really far, and that nearly all aspects of fertility in yogurt-eating male mice had been enhanced.

“There were legitimate physiological differences in males fed probiotics, not just the extra sexiness,” Erdman added.

Male mice also had coats that were10 times thicker and “shockingly shiny” compared to mice on other diets.

Besides having greater reproductive success, researchers from the latest unpublished study believe that the probiotic microbes in the yogurt help animals become leaner and healthier, indirectly improving their “sexual machismo,” according to Scientific American.