For years, the prevailing scientific understanding was that abdominal fat — the absolute amount of it in a person– was the primary risk factor for conditions like diabetes and heart disease. But a study released on Thursday reveals that the proportion of other types of body fat is also a critical factor in assessing health risks. The findings suggest that healthcare providers should not only focus on losing weight, but changing how fat is distributed in the body, according to The Press Service of Israel (TPS-IL).

Researchers from Ben-Gurion University of the Negev working in collaboration with researchers from Harvard, Leipzig, and Tulane Universities discovered that both the proportion of intra-abdominal fat relative to subcutaneous fat and the absolute amount of intra-abdominal fat are risk factors.

“Two people with the same BMI can have completely different metabolic risks depending on their visceral fat distribution. Our study shows that these differences are important in assessing cardiometabolic risk,” explained PhD student Hadar Klein, the study’s lead author.

Intra-abdominal fat and visceral fat are essentially the same thing. Both refer to fat stored around internal organs in the belly, like the liver and intestines. “Intra-abdominal fat” is a broader term that includes all fat in the abdominal area, while “visceral fat” specifically refers to the fat around the organs. Subcutaneous fat refers to fat stored just beneath the skin and is the fat people can pinch with their fingers. Unlike visceral fat, which surrounds internal organs, subcutaneous fat is less harmful and can even have protective benefits for the body.

By targeting visceral fat, even without major weight loss, people can significantly reduce their risk of disease, the researchers said.

The study, led by Prof. Iris Shai from Ben-Gurion University, involved approximately 600 participants and used advanced MRI technology to examine how intra-abdominal fat relates to metabolic health. The study was recently published in the peer-reviewed BMC Medicine.

The team analyzed data from two 18-month clinical trials of dietary supplements. These trials tested Mediterranean diets, with or without nuts, green tea, and manka beans, with or without exercise, compared to control diets in 572 participants, an unprecedented number in size. MRI scans were also performed before and after the experiment.

After 18 months of testing, participants (mostly men) lost an average of 23% of their abdominal fat area, and the proportion of abdominal fat decreased from 28.2% to 26.9%

Through various blood tests, the researchers were able to identify participants’ quality and quantity of fat before and after they lost weight.

Before the participants lost weight, the scientists found that people who had relatively, proportionally, more intra-abdominal fat, compared to total abdominal fat — even if they were leaner — had higher levels of blood fats, a key marker of metabolic disorder.

On the other hand, people who had more intra-abdominal fat area were found to have higher levels of the protein CRP – a marker associated with chronic inflammation, and higher levels of glycated hemoglobin ( HbA1c)), which is related to sugar control.

These findings suggest that high blood lipid levels — even in apparently thin people — may reflect a high proportion of intra-abdominal fat in the belly. In contrast, markers associated with chronic inflammation and diabetes may reflect a high amount of intra-abdominal fat in people with large waist circumferences, the researchers said.

Both reducing the proportion of intra-abdominal fat (relative reduction) and decreasing its total amount (area reduction) led to significant improvements in blood lipid levels, glucose control, and liver function.

The findings could lead to more personalized weight loss programs, especially for individuals with a higher proportion of intra-abdominal fat, regardless of their overall weight. The research reinforces the importance of dietary changes in reducing intra-abdominal fat, even without significant weight loss.

The study also suggests that doctors assess both the total amount and proportion of intra-abdominal fat when evaluating metabolic risk. This could involve using MRI in routine screenings for individuals at risk, even those who are not overweight but have unhealthy fat distribution.