Low-Carbohydrate or Low-Fat Diet: which one for weight loss and heart health? (2014-09-06)

Low-carbohydrate diets are popular for weight loss, but their cardiovascular effects have not been well-studied, particularly in diverse populations.

To examine the effects of a low-carbohydrate diet compared with a low-fat diet on body weight and cardiovascular risk factors researchers recruited 148 obese men and women between the ages of 22 and 75, without clinical cardiovascular disease and diabetes.

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All participants attended regular meetings where they learned about portion control, healthy eating and overall nutrition. They were also offered one meal-replacement bar or shake per day and they were told to not change their physical activity throughout the trial.

Those in the low-carbohydrate group were told to eat at no more than 40 grams of digestible carbohydrates per day. ("Digestible carbs" equals total carbs minus total fiber.)

Those in the low-fat group were told not to get more than 30 percent of their daily energy from fat and no more than 55 percent of their daily energy from carbohydrates.

Overall, about four of every five participants were still following the diets 12 months later.

Both groups received dietary counseling at regular intervals throughout the trial.

Data on weight, cardiovascular risk factors, and dietary composition were collected at 0, 3, 6, and 12 months.

During that time, the researchers found, people on the low-carbohydrate diet lost more weight and more body fat than those on the low-fat diet.

Sixty participants (82%) in the low-fat group and 59 (79%) in the low-carbohydrate group completed the intervention. At 12 months, participants on the low-carbohydrate diet had greater decreases in weight (mean difference in change, -3.5 kg [95% CI, -5.6 to -1.4 kg]; P = 0.002), fat mass (mean difference in change, -1.5% [CI, -2.6% to -0.4%]; P = 0.011), ratio of total–high-density lipoprotein (HDL) cholesterol (mean difference in change, -0.44 [CI, -0.71 to -0.16]; P = 0.002), and triglyceride level (mean difference in change, -0.16 mmol/L [-14.1 mg/dL] [CI, -0.31 to -0.01 mmol/L {-27.4 to -0.8 mg/dL}]; P = 0.038) and greater increases in HDL cholesterol level (mean difference in change, 0.18 mmol/L [7.0 mg/dL] [CI, 0.08 to 0.28 mmol/L {3.0 to 11.0 mg/dL}]; P < 0.001) than those on the low-fat diet.

The low-carbohydrate diet was more effective for weight loss and cardiovascular risk factor reduction than the low-fat diet. Restricting carbohydrate may be an option for persons seeking to lose weight and reduce cardiovascular risk factors.

Researchers said they are not sure why people on the low-carbohydrate diets lost more weight and had lower risk factors for heart disease after one year. It's not clear, she added,if there would still be a difference after a longer period.

For more information
Annals of Internal Medicine, online September 1, 2014
Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial

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