If the person had clogged arteries and high blood pressure, then went on a healthy diet, the person would start losing weight. They would have a more stable blood pressure (since they are eating healthy foods, with less saturated fat) and the clogged arteries would look significantly better. He/she might lose her/his risk of developing diabetes, heart disease, cancer, etc. Most of her/his health issues would start to balance out if they started eating a diet low in saturated fat.
I hope this helps!
~kaikers
