Abdominal visceral fat can disrupt the 24-hour circadian rhythms of the body by disturbing the body’s clock genes, a local study showed Friday.

The research team led by Lee Ji-won, a professor of family medicine at Gangnam Severance Hospital, said it found that “visceral fat rather than subcutaneous fat affects clock genes.”

The circadian rhythm is a body rhythm of creatures, including humans, moving regularly for 24-25 hours according to the rotation of the earth. Humans are hungry in time and wake up in the morning without a clock, thanks to the circadian rhythm. Clock genes control the circadian rhythms to work correctly.

If the circadian rhythm breaks down, energy metabolism does not function well, leading to obesity, inflammation, and increase in metabolic diseases. Obesity itself can disrupt clock genes and changes the circadian rhythm, researchers have suggested.

And the local research team has discovered that abdominal visceral fat confuses the circadian rhythm.

The study was on 75 men and women who visited the Gangnam Severance Hospital’s obesity clinic, measuring the area of visceral fat and subcutaneous fat by abdominal (CT) scans. Then, the researchers extracted gene clocks from peripheral blood mononuclear cells to detect gene expression.

Results showed that the larger the visceral fat area, the levels of PER2, PER3, CRY2 mRNA in clock genes decreased, and CRY1 mRNA levels increased. Even after adjusting confounding variables, the visceral fat had an independent association with the BMAL1, PER2, CRY1 mRNA levels. However, the subcutaneous fat area did not show correlation with any of the genes.

That is, it was visceral fat, not subcutaneous fat, that affected clock genes, the study showed.

“As the study showed that visceral fat was correlated with the expression of clock genes, we need further research on how clock genes affect visceral fat-related diseases such as cardiovascular and cerebrovascular disease and cancer,” Professor Lee said.

The study was published in international academic journal Chronobiology International.