The little-known oil which could be driving obesity – and is in more foods than you think

One of the most common vegetable oils found in processed foods may contribute to weight gain due to the way it is processed in the body, a new study has suggested.

Although not generally used as a base in cooking, soybean oil is often found in processed foods such as salad dressings, margarine, and chips. Previous research has linked soybean oil to weight gain, but it wasn’t clear why it caused some people to gain weight.

New research from scientists at the University of California, Riverside, has found that the way fat is processed in the body, rather than the fat itself, can lead to weight gain when eaten in excess.

“Soybean oil is not inherently bad,” said Frances Sladek, a professor of cell biology at the university. “But the amounts we consume it in trigger pathways that our bodies cannot cope with.”

Researchers fed two groups of mice a diet rich in soybean oil to understand why it promotes obesity more than other fats. While no genetic changes were made in the first group, a slightly different form of liver protein was produced in the second group, which affects how the body metabolizes fats.

They found that the first group gained a significant amount of weight, but the second group did not; This suggested that genetics and modern diets play an important role in obesity.

“This may be the first step towards understanding why some people gain weight more easily than others on a diet rich in soybean oil,” said Sonia Deol, a biomedical scientist at the university and corresponding author of the study.

The study builds on previous work by researchers that linked soybean oil to weight gain. “We have known since our study in 2015 that soybean oil is more obesogenic than coconut oil,” Prof Sladek said. “But we now have the clearest evidence that it’s not the fat itself, or even the linoleic acid. It’s what the fat turns into in the body.”

Linoleic acid is an important fatty acid found in soybean oil that the body converts into molecules called oxylipins. Excessive consumption of linoleic acid can lead to increased amounts of oxylipin, which is associated with inflammation and fat accumulation.

The genetically modified mice in the study had significantly less oxylipin and showed healthier livers despite eating the same high-fat soybean oil diet as normal mice. They also showed signs of improved mitochondrial function, which may help explain their resistance to weight gain.

The analysis also showed that the genetically modified mice had much lower levels of two key families of enzymes responsible for converting linoleic acid into oxylipins.

Although no human trials are planned, the team hopes these findings will guide future research and inform nutrition policy.

“It has taken 100 years since the first link between chewing tobacco and cancer was first observed to put warning labels on cigarettes,” Prof Sladek said. “We hope it won’t take so long for society to realize the link between excessive soybean oil consumption and adverse health effects.”