Question: What are the roles of diet and exercise in determining cholesterol levels?
Answer: Diet is an extremely important maneuver to lower LDL or bad cholesterol. Here we generally restrict saturated fats, we restrict trans fats, and we also make recommendations for cholesterol restriction. For most Americans at moderate to higher risk, it's recommended that percentage of calories coming from saturated fats should be less than seven percent of total calories. And for trans fat, you know the food labels are really great these days because they tell you if trans fats are free in the food or present in the food. We should be as trans fat free as we can. So that would be an estimated less-than-one percent of total calories that's trans fat.
Dietary cholesterol, which is usually linked with saturated fats, is sometimes separated from saturated fats in egg yolks and in shellfish. But dietary cholesterol restriction has a lesser impact on our bad cholesterol levels than restrictions in saturated and trans fat.
Now exercise is an important venue for modifying our lipoprotein cholesterol levels. But here, exercise's effects on LDL are modest. Exercise really doesn't change the bad cholesterol much at all. But people who are well trained and exercising regularly tend to have higher levels of the good cholesterol HDL. And that may be one mechanism by which having a physically active lifestyle reduces the risk for cardiovascular disease and stroke.