Abstract

When considering dietary fat quantity, there are two main factors to consider, impact on body weight and plasma lipoprotein profiles. Data supporting a major role of dietary fat quantity in determining body weight are weak and may be confounded by differences in energy density, dietary fiber, and dietary protein. With respect to plasma lipoprotein profiles, relatively consistent evidence indicates that under isoweight conditions, decreasing the total fat content of the diet causes an increase in triglyceride and decrease in high-density lipoprotein (HDL) cholesterol levels. When considering dietary fat quality, current evidence suggests that saturated fatty acids tend to increase low-density lipoprotein (LDL) cholesterol levels, whereas monounsaturated and polyunsaturated fatty acids tend to decrease LDL cholesterol levels. Long-chain omega-3 fatty acids, eicosapentaenoic acid (EPA) (20:5n-3) and docosahexaenoic acid (DHA) (22:6n-3), are associated with decreased triglyceride levels in hypertriglyceridemic patients and decreased risk of developing coronary heart disease (CHD). Dietary trans-fatty acids are associated with increased LDL cholesterol levels. Hence, a diet low in saturated and trans-fatty acids, with adequate amounts of monounsaturated and polyunsaturated fatty acids, especially long-chain omega-3 fatty acids, would be recommended to reduce the risk of developing CHD. Additionally, the current data suggest it is necessary to go beyond dietary fat, regardless of whether the emphasis is on quantity or quality, and consider lifestyle. This would include encouraging abstinence from smoking, habitual physical activity, avoidance of weight gain with age, and responsible limited alcohol intake (one drink for females and two drinks for males per day).