Low-fat and low-carb diets: cardiovascular disease risk comparison

Low-fat or Low-Carb Diets: Which is healthier?

This study looked at several factors relating to cardiovascular disease including weight and low and high density lipoproteins to determine whether low-fat or low-carb diets were healthier. Low-fat diets were determined to be the healthier choice of the two.

Cardiovascular disease (CVD) is a term that refers to many diseases that affect the heart and blood vessels such as hardening of the arteries, arrhythmia and heart attack. According to MayoClinic.com it is the number one world wide killer of both men and women and is the cause of 40% of deaths in the U.S. alone.

There are several factors that determine a person's risk for CVD. These include diet, weight and genetic factors. Diet is an important factor. Low-fat diets restrict fat and cholesterol intake. Doctors have recommended low-fat diets as a way to reduce CVD risk. Low-carb diets limit the intake of carbohydrates such as grains. The low-carb diet has become a popular diet for losing weight. Which diet is a healthier choice? In this study, several measures were used to determine whether CVD symptoms were increased or decreased with either low-fat or low-carb diets.

Materials and Methods

Nurses' Health Study -- 84,129 women's diets were studied between 1980 and 1994. Diets were given a score ranging from 1 to 5. A score of 1 indicated an unhealthy diet and 5 indicated a healthy diet high in fiber and omega-3 fatty acids. A relative risk score was calculated by comparing a person's chance of having CVD symptoms to that of women with a score of 5.

Framingham Study -- 2,489 men ranging in age from 30 to 74 years of age were studied for CVD symptoms for twelve years. Low and high density lipoproteins (LDL and HDL) were measured.

Six-month and Twelve-month Diet Studies -- In the six-month diet study 120 obese men and women were restricted to either a low-fat or a low-carb diet. The participants ranged in age from 18 to 65 and 79 finished the study. In the twelve-month diet study 132 severely obese men and women were restricted to either a low-fat or a low-carb diet. All participants were 18 years or older and 87 completed the study. In both studies, weight was measured at zero and six months with an additional twelve-month measurement recorded for the twelve-month study. Also, LDL and HDL were measured in both studies at the beginning and the end of the study. The low-fat diet for the six-month study consisted of 100-500 calories below the daily requirements with only 30% coming from fat and only a total of 30 mg of cholesterol. The low-fat diet of the twelve-month study was defined as 500 calories below the daily requirements with only 30% coming from fat. The low-carb diets consisted of 20 g of carbohydrates a day and nutritional supplements for the six-month study and 30 g of carbohydrates for the twelve-month study. All participants received nutritional counseling.

Discussion

The low-fat diet is healthier. Both groups exhibited weight loss. However, in the low-carb diet weight was gained back in the longer term study. In the low-fat diet weight loss was slow but steady, which is healthy.

Also, the low-fat diet caused decreases in bad cholesterol with only a small decrease in healthy cholesterol, whereas the low-carb diet increased bad cholesterol and decreased good cholesterol. Although CVD risk was not lessened with the low-fat diet within one year, it is possible that with slow and steady changes in weight and cholesterol levels that it would over a greater time period. Further studies would be needed to test this hypothesis. The low-carb diet did lower CVD risk in a short-term study, but had no effect on CVD in the one-year study. This potential yo-yo effect in weight loss and CVD risk caused by the low-carb diet is unhealthy.