Is Excess Soybean Oil in the Food Supply a Factor in Obesity?

Soybean oil is the most common cooking oil in the American food supply. By far. If you are consuming a lot of ultra-processed foods, you are consuming a lot of soybean oil. Now, the University of California at Riverside says that a new study links soybean oil to obesity.

Specifically, scientists at the university have published research to detail a metabolic pathway that explains weight gain in mice who consume an excess of soybean oil. Their work appears in the Journal of Lipid research.

Mice That Resist Gaining Weight from Soybean Oil

Researchers at UC-Riverside have been pursuing the possibility of a link between soybean oil and obesity for some time now. Frances Sladek, a professor of cell biology and senior author of this new research, says:

“We’ve known since our 2015 study that soybean oil is more obesogenic than coconut oil. But now we have the clearest evidence yet that it’s not the oil itself, or even linoleic acid. It’s what the fat turns into inside the body.”

They showed this with genetically altered mice that resist gaining weight from soybean oil as normal mice do. These mice became resistant to that weight gain because they did not have adequate enzymes to efficiently convert the linoleic acid in soybean oil into a molecules called oxylipins. The authors of this research conclude that some of these oxylipins are “potential drivers of obesity.” Their absence in these altered mice seems to make them resistant to weight gain from soybean oil consumption.

A Long Way to Evidence for Causality in Humans

But let’s be clear. As appealing as this story is, it is still a long way from this metabolic pathway in genetically altered mice to evidence for soybean oil causing obesity in humans.

In a recent systematic review and network meta-analysis, Shima Abdollahi and colleagues found “low to moderate certainty of evidence” that soybean oil is associated with weight gain. But there are significant issues with methodology, study quality, heterogeneity, and study duration in the available studies.

Available evidence simply does not point to soybean oil causing significantly more weight gain than other oils when you control for caloric content. Furthermore, because soybean oil is predominantly found in low-quality, highly-processed foods, it seems that its consumption may be as much or more of a marker for a low-quality diet than it is a problem all by itself.

So, yes, this research in mice is interesting for understanding potential metabolic pathways that might come into play with overconsumption of soybean oil. But it hardly proves that soybean oil is a driver of our excess obesity prevalence.

Click here for the study, here and here for further perspective on it. For further perspective, click here and here.

Edamame Soybean Blossom, photograph by Anders Croft for the USGS / Wikimedia Commons

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December 1, 2025