Mice fed soybean oil had significant increases in weight gain, body fat, diabetes, glucose intolerance, and insulin resistance compared to those fed coconut oil. The soybean-oil diet was also found to upregulate genes involved in obesity, diabetes, inflammation, mitochondrial function, and cancer. In one study when heart-disease patients replaced saturated animal fats with omega-6 vegetable oils like soybean oil it led to an increased risk of death.
Scientists in California published a study investigating the effects of saturated versus unsaturated fat in the diets of mice, as well as fructose, on obesity and diabetes. The unsaturated fat was soybean oil, and the saturated fat was coconut oil, along with a fructose. Soybean oil came out the clear loser when looking at the dietary effect on obesity and diabetes.