Earlier this month, University of Copenhagen researchers published a study that suggested overweight fathers may pass down obesity to their children.

The idea of inheriting a predisposition for obesity isn’t anything new—as scientists have long known that genetics does play a role in obesity (although how big of a role that plays in comparison to overeating, lack of exercise, or socioeconomic factors is widely debated).

What makes this study unique, however, is that researchers suggested that a man’s eating habits might be passed down to his children. His genetic code doesn’t change—but certain genes in his sperm may be expressed or silenced based on his experiences and environment. The molecules that turn on and turn off genes are called epigenetic markers.

Related: Hey, Men: Your Diet Might Hurt Your Future Kids

In the study published in the journal Cell Metabolism, researchers took sperm samples from six obese men before and after they had their stomachs stapled to induce rapid weight loss (also known as gastric bypass surgery).

Just one week following the surgery, they found that epigenetic markers in the volunteers’ sperm had changed. In fact, researchers noticed epigenetic changes in the genes that actually affect appetite control.

However, the study doesn’t tell us whether or not those changes will affect the volunteer’s children—since those volunteers obviously need to procreate after the surgery before we would know anything.

“We know for certain that the epigenetic signature of human sperm cells changes if losing weight after bariatric surgery, or exercising (data not published yet), but what we still lack to investigate is whether these changed epigenetic patterns of the sperm cells also affects the health of the next generation,” one of the study’s researchers, Ida Donkin, wrote in a Reddit Ask Me Anything session earlier this week.

Numerous animal studies, however, suggest that those changes are passed down to offspring—whether that happens in humans remains to be seen. But Donkin did reference a 2014 study in which the offspring of male rats exposed to stressful experiences inherited the same stress responses as their parents.

Donkin wrote:

“If you repeatedly expose a male mice to electric shocks simultaneously with the smell of acetone he would naturally, after a while, develop a shock response just when experiencing the pure smell of the acetone. Surprisingly, his sperm cells will change their epigenetic pattern in response to this, and his children will also react with a stress response when smelling acetone – telling us that the experience of electric shock has been transferred forward to the next generation.”

In the case of obesity, we don’t whether losing weight will positively or negatively affect offspring, says Romain Barrès, another researcher on the team.

“Maybe the changes we see in obesity are transmitted to children and DECREASE appetite. Maybe. And that would mean that epigenetic transmission is a GOOD thing that could be overwritten by environmental factors in the life of the offspring,” he wrote.

The researchers hope to find out exactly how epigenetic markers affects the offspring of humans in a related study.

“We are currently investigating pregnant couples and matching up the parent’s epigenetic signature to the epigenetic signature of the newborn’s stem cells, to see exactly what patterns are being transferred to potentially affect the health of the offspring,” said Donkin.