Saturated fats and trans fats are considered unhealthy and should be limited in the diet due to their links to increased cholesterol levels and higher risk of cardiovascular diseases. Saturated fats are commonly found in animal products and certain oils, while trans fats are typically present in partially hydrogenated oils used in processed foods. Limiting these unhealthy fats and replacing them with healthier options, such as unsaturated fats from nuts, seeds, and olive oil, can support heart health and lower the risk of chronic diseases.