Why are some of us addicted to sugary sweets and treats? A new study says gene variants may be the culprit.

Researchers at the University of Copenhagen analyzed data from 6,514 Danish people already participating in a larger heart disease study, Inter99 cohort. They also looked through participants’ responses on their dietary preferences, and examined results from cholesterol and glucose tests.

Previous research conducted in 2015 showed the FGF21 gene was associated with food regulation in mice and nonhuman primates, but the new study suggests the gene plays a similar role in human appetite as well.

The researchers found that participants who had one of two variants of the FGF21 gene were about 20 percent more likely to crave sugary snacks like candy, ice cream and cake. But those who reported that they disliked sweets had elevated FGF21 levels.

The study also revealed a potential association between the gene variants and increased alcohol intake and daily smoking, but more research needs to be conducted to validate that connection, the authors said.

However, the study did not observe a link with FGF21 gene variants and obesity or diabetes, which came as a bit of a surprise.

"Dozens of factors have been found to be involved in metabolic disease. In this study, we are just looking at one little piece in a big puzzle," said Niels Grarup, co-lead investigator.

The liver secretes FGF21 after sweets have been consumed, but the researchers believe the liver may also secrete other hormones that guide our overall food choices.

"How do we decide what and how much to eat? Maybe satiety consists of different pathways that control different types of nutrients," said Matthew Gillum, assistant professor of biological sciences and co-lead investigator with Grarup. "This study has opened my mind to how this regulatory system might work."

Grarup and Gillum also conducted a small clinical study to better evaluate the flow of FGF21 in the blood of 51 volunteers in response to sugar intake. Participants were either the most extreme cravers of sweets, or greatly disliked sweets.

The group fasted for 12 hours, and then had their FGF21 levels measured. The researchers then monitored changes in FGF21 levels over five hours after participants drank water with about the same amount of sugar found in two cans of Coke.

Those who disliked sweets had fasting FGF21 blood levels 50 percent higher than their sweet-toothed counterparts. But after the sweet drink, FGF21 blood levels followed the same trajectories and rose to about the same levels in both groups.

Garup and Gillum hope to replicate the study in a larger group of humans to better understand how the behavior of FGF21 varies between individuals.

The study was published in Cell Metabolism.