**Abstract**

Diet is a foundation of treatment for lifestyle-related diseases, such as high blood pressure, diabetes, and dyslipidemia. For these diseases, diet therapy has been disregarded in management of hyperlipidemia. Fat has more diversity of biological effects compared to those of protein and carbohydrate. New emerging evidences have resulted in a clear shift of recognition of fatty acids in diet therapy. The PREDIMED study has shown recently the amazing result that a calorie-unlimited, high-fat Mediterranean diet caused about 30% reduction in cardiovascular disease in obese subjects compared with a low-fat diet. Many authorities have removed restriction of intake of fat from their guidelines. The important, new message from recent medical and nutritional science is that people need to consume more "good fat" rather than limiting intake of fat to prevent cardiometabolic diseases. In this chapter, I would like to focus on the role of fatty acids with special relation on their effects on blood lipids and cardiovascular events.

**Keywords:** saturated fat, unsaturated fat, complex and refined carbohydrate, Mediterranean diet, olive oil, n-3 fish oil, primary and secondary prevention, LDL cholesterol, antioxidant, diet guidelines

## **1. Introduction**

Diet therapy has been disregarded in management of hyperlipidemia. Statistical data for the US between 1990 and 2016 show that in addition to tobacco consumption, poor diet and subsequent obesity are one of the major reasons for mortality [1]. Generally, information about the benefits of nutritional interventions has not adequately been translated into action in medical training or practice [2]. In a 2017 online survey of 646 cardiologists in the US [3], 90% reported that they had not received adequate nutrition education to be able to counsel their patients, even though 95% believed it was their personal responsibility to do so.

Compared with pharmacological trials, high-level evidence about diet therapy is limited. Among the three macronutrients, data around fat have been especially controversial. This is partially due to the more diverse roles of fat compared to protein or carbohydrate. Fat is not only a source of energy production but also a major component of hormones, and cell and nuclear membranes, and a carrier for the fat-soluble vitamins. Furthermore, essential fatty acids are involved in many physiological processes such as inflammation, cell proliferation, wound healing, and blood coagulation. The data about diet therapy are frequently inconsistent even for apparently solid recommendations in authorized guidelines. In this chapter, I would like to focus on the role of fatty acids with special relation on their effects on blood lipids and cardiovascular events.

mortality among 5145 obese patients with type 2 diabetes [8]. The intensive lifestyle intervention was aimed at achieving and maintaining weight loss of at least 7% by focusing on reduced caloric intake (calorie goal of 1200–1800 kcal per day, restricting fat calories to <30%) and increased physical activity. Although greater reductions in all CV risk factors was observed in the intervention group than in the control group, the rate of CV mortality and myocardial infarction was not different (**Figure 1a**). Rebound of weight in the intervention group (**Figure 1b**) increased the statin use in the control group, and the lack of instruction about saturated and unsaturated fats is suggested for reasons of the negative results in this study. Five years later, in the PREDIMED study [6], a Mediterranean diet loaded with high content of monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUSA) without calorie restriction and exercise recommendation reduced CV events significantly approximately by 30% compared to the control low-fat diet group (**Figure 2**). It is noteworthy that the reduction of CV events occurred in the Mediterranean diet groups that consumed about 200–250 kcal higher calories as fat

*Effects and Issues of Diet Fat on Cardiovascular Metabolism*

*DOI: http://dx.doi.org/10.5772/intechopen.93261*

than in the control group. The data of these two studies [6, 8] have strongly

lying disease, BMI, and daily diet habits.

**Figure 1.**

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suggested that intake of unsaturated fat is more effective than a low-fat, low-calorie diet for reduction of CV events. However, weight reduction by the low-fat diet in the LookAHEAD study has brought in important health benefits other than CV event reduction. Patients in the low-fat group were more likely to have a partial remission of diabetes during the first 4 years of the trial [9], more improvement in terms of reductions in urinary incontinence [10], sleep apnea [11], and depression [12] and improvements in quality of life [12], physical functioning [13], and mobility [14] than were those in the control group. Calorie restriction by diet is effective in reducing body weight in obese subjects. Therefore, diet therapy should be individualized dependent on the treatment goal, patient's characteristics such as under-

The difference in LDL cholesterol in the two groups in the LookAHEAD study was 1 mg/dl at the end of study [8]. By contrast, the effects of bariatric surgery on plasma LDL cholesterol and CV events have been clearer, because bariatric surgery reduces body weight to a greater extent, 20–40% from baseline. In a study of registry data in Sweden, LDL cholesterol was reduced approximately 40% associated with a 30% decrease in all-cause mortality 15 years after the surgery [15].

*(a) Kaplan-Meier curves of the primary end point in look AHEAD study [8]. The primary outcome was a composite of death from cardiovascular causes, nonfatal myocardial infarction, nonfatal stroke, or*

*hospitalization for angina. (b) Changes in body weight in the look AHEAD study [8].*
