There are few studies examining the effects of a diet low in carbohydrates on cardiovascular disease (CVD) risk factors in the long term, particularly in contrast to the current dietary recommendations for decreased fat intake to reduce risk of CVD. We recruited 148 study participants with a body mass index (BMI) of 30–45 kg/m2, who were free of diabetes, CVD and kidney disease at baseline and randomly assigned them (74 in each group) to either a low carbohydrate diet (<40 g/day) or a low fat (<30% energy from fat, <10% from saturated fat) diet. Participants met with a study dietitian weekly for the first month then in group settings bi-weekly for 5 months then monthly for the next 6 months. Each group was provided the same behavioral curriculum related to diet emphasizing portion control and eating habits. Two 24-hour dietary recalls were conducted at each clinic visit (0, 3, 6 and 12 months of intervention). The primary outcome measures were weight, body composition, lipids, blood pressure, and glucose. Mean age of participants was 46.8 years, mean BMI was 35.4 kg/m2; 11.5% were men, and 51% were African-American. Of the study participants, 60 in the low fat group (81.1%) and 59 in the low carbohydrate group (79.7%) completed the entire intervention. At 12 months, mean total energy intake on the low carbohydrate diet was 1,448 kcal/day with 23.6% from protein, 40.7% from fats, and 34.0% from carbohydrate versus 1,527 kcal/day with 18.6% from protein, 29.8% from fats, and 50.0% from carbohydrate on the low fat diet. Compared to low fat diets, over 12 months the low carbohydrate group had greater reductions in weight (net change −3.62 kg, p<0.001), fat mass (−2.83 kg, p<0.0001), waist circumference (−1.79 cm, p=0.03), triglycerides (−12.83 mg/dL, p=0.05), and a greater increase in high density lipoprotein cholesterol (HDL-C, 6.74 mg/dL, p<0.001). There were no differences in net changes between diets for total cholesterol, low density lipoprotein cholesterol, blood pressure, glucose, creatinine, or lean body mass. Our findings document that a low carbohydrate diet was more effective for weight loss than a low fat diet, and did not have significant adverse effects on cardiovascular risk factors. In contrast, the low carbohydrate diet improved HDL-C and triglycerides as compared to a low fat diet. Restricting carbohydrates is an effective method of weight loss and could be recommended for persons with and without increased CVD risk factors who need to lose weight.
A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet on Body Weight and Cardiovascular Risk Factors in Healthy Women