Methods
This study focused on all published in-vivo and human studies regarding thermally degraded vegetable oils and their adverse effects which fulfilled all of the following criteria: (1) original data for dietary interventions using thermally oxidized palm oil (PO), corn oil (CO), canola oil (CNO), extra virgin olive oil (EVOO), sunflower oil (SFO) and soybean oil (SBO) (inclusive of diets with repeatedly heated plant oils as well); (2) Must include a control group of either a normal diet with unheated vegetable oils or a basal diet (fed with only rat chow); (3) the mean ± standard deviation values of weight gain, BMI (kg/m2), adipose tissue, low-density lipoprotein (LDL) cholesterol, the thickness of artery wall, liver thiobarbituric acid reactive substances (TBARS) and homeostatic model assessment of insulin resistance (HOMA-IR) were reported. We excluded studies that used (1) any other vegetable oil that was not mentioned above; (2) a mixture of vegetable oil in the diet; (3) modified oil that chemically interesterified, enzymatically interesterified, or hydrogenated.