Trans-fats are unsaturated fatty acids that come from industrial or natural sources. They clog arteries, increasing heart attack risk. WHO suggests healthier alternatives like monounsaturated and polyunsaturated fats. Monounsaturated fats are found in sesame seeds, peanuts, almonds, hazelnuts and olive/canola/avocado oils. Polyunsaturated fats are found in several fish, walnuts and vegetable oils.