Olive oil is often praised for its health benefits, but a new study suggests that consuming too much of it—specifically, the fatty acid called oleic acid—might actually lead to weight gain.
The research, published in the journal Cell Reports, found that oleic acid can encourage the body to create more fat cells, which may increase the risk of obesity and related health problems.
Oleic acid is a type of monounsaturated fat found in large amounts in olive oil.
While it’s commonly considered a healthier fat compared to others like saturated fat, this study raises concerns about how it affects the body when consumed in high amounts.
Researchers from the University of Oklahoma, Yale University, and New York University fed mice different diets, each high in a specific type of fat.
These fats came from sources like coconut oil, peanut oil, milk, lard, and soybean oil.
Oleic acid stood out—it was the only fat that caused an increase in the number of early-stage cells that grow into fat cells.
Dr. Michael Rudolph, a professor at the University of Oklahoma College of Medicine, explained that this increase in fat cell growth could lead to a greater ability to store extra calories. Over time, this may raise the chances of becoming obese, which in turn increases the risk for heart disease and diabetes.
He compared fat cells to an army: “When you eat a lot of oleic acid, it’s like adding more soldiers to your fat cell army.
That creates more room to store fat. But if you keep eating more than your body needs, even the extra fat cells can’t keep up, and that’s when weight gain and health issues start.”
Although people don’t usually eat just one type of fat—meals are typically a mix of many kinds—Rudolph pointed out that diets high in oleic acid are becoming more common, especially with the rise of fast food and processed foods.
The key takeaway? Eating fat isn’t bad, but balance matters. Getting fats from a variety of sources is healthier than relying too much on one type—even one as popular as olive oil. According to Rudolph, while moderate amounts of oleic acid are fine, high and long-term intake may not be the best choice, especially for people at risk of heart problems.
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