New research suggests that soybean oil cause more obesity than a high fructose diet.

An animal study conducted by researchers at the University of California at Riverside showed that mice on high soybean diet had increased levels of weight gain and diabetes compared to mice on a high fructose diet or high coconut oil diet.

"This was a major surprise for us - that soybean oil is causing more obesity and diabetes than fructose - especially when you see headlines everyday about the potential role of sugar consumption in the current obesity epidemic," researcher Poonamjot Deol said in a statement.

In the U.S. the consumption of soybean oil has increased greatly in the last four decades due to a number of factors, including results from studies that encouraged people to reduce their intake of saturated fats, commonly found in meat and dairy products, and increase their intake of polyunsaturated fatty acids found in plant oils, such as soybean oil.

For the study, researchers fed mice a series of four diets that contained 40 percent fat, similar to what Americans currently consume. In one diet the researchers used coconut oil, which consists primarily of saturated fat. In the second diet about half of the coconut oil was replaced with soybean oil, which contains primarily polyunsaturated fats and is a main ingredient in vegetable oil. That diet corresponded with roughly the amount of soybean oil Americans currently consume.

They found that mice on the soybean oil-enriched diet gained almost 25 percent more weight than the mice on the coconut oil diet and 9 percent more weight than those on the fructose-enriched diet. And the mice on the fructose-enriched diet gained 12 percent more weight than those on a coconut oil rich diet.

Compared to mice on the high coconut oil diet, mice on the high soybean oil diet showed increased weight gain, larger fat deposits, a fatty liver with signs of injury, diabetes and insulin resistance. These are all associated with metabolic syndrome, a cluster of abnormalities associated with the development of cardiovascular disease and type 2 diabetes.

Fructose in the diet had less severe metabolic effects than soybean oil although it did cause more negative effects in the kidney and a marked increase in prolapse

The findings are detailed in the journal PLOS One.