Hidden fat deposits packed around abdominal organs like the stomach, intestines and liver could be increasing people’s risk of heart disease, a new study says.

Excessive amounts of this hidden fat — also called visceral fat — is tied to faster aging of the heart, researchers report in the European Heart Journal.

This fat can’t be seen from the outside, and some people can have large amounts of visceral fat even if they have a healthy weight, researchers noted.

“Our research shows that ‘bad’ fat, hidden deep around the organs, accelerates aging of the heart,” senior researcher Dr. Declan O’Regan, a professor at the MRC Laboratory of Medical Sciences at Imperial College London, said in a news release.

“But some types of fat could protect against aging — specifically fat around the hips and thighs in women,” he added.

For the study, researchers analyzed data from more than 21,000 participants in the UK Biobank, a large-scale health research project taking place in the United Kingdom.

MRI scans were used to detect fat deposits in participants’ bodies, and to examine their heart and blood vessels. Each person was given a “heart age” — the apparent age of their heart and circulatory system given signs of wear and tear.

Results showed that faster heart aging was linked to having more visceral fat deep inside the organs. 

“While being active is important, we found that hidden fat could still be harmful even in fit people,” O’Regan said.

Blood tests indicated that visceral fat is linked to increased inflammation in the body, which might cause this premature aging.

The results also pointed to differences between men and women.

“Apple-shaped" fat distribution around the belly was strongly related to accelerated heart aging in men.

But “pear-shaped" distribution on the hips and thighs appeared to protect women against heart aging. These fat deposits are known to produce the female hormone estrogen, and higher levels of estrogen are associated with slower heart aging in women, researchers said.

“We have known about the apple and pear distinction in body fat, but it hasn't been clear how it leads to poor health outcomes,” O’Regan said.

The study also found body mass index (BMI) lacking as a means of tracking heart health. BMI is an estimate of body fat based on height and weight.

“We also showed that BMI wasn’t a good way of predicting heart age, which underscores the importance of knowing where fat is stored in the body and not just total body weight,” O’Regan said.

Researchers next plan to see whether weight loss through use of GLP-1 drugs like Ozempic might affect visceral fat deposits and heart health effects.