Debate Says Low-Carb Diet Advantageous Over Low-Fat
Over the years, doctors, dietitians and other health professionals have strived to find the perfect blend of macronutrients (ie carbohydrate, fat and protein) that would constitute the most healthful diet. Unfortunately, the optimal diet is more than just these three nutrients and scientists are still looking for a plan that Americans can easily follow to help with the most pressing health problems in our society – obesity and heart disease.
Low Carb vs Low Fat Diets
The latest debate between low-carb and low-fat diets has found that they are equally good for long-term weight control, but low-carb diets may have a slight advantage over certain risk factors, such as HDL cholesterol and blood pressure.
Researcher Dr. Gary D. Foster, director of the Obesity Research and Education Center at Temple University in Philadelphia studied 307 middle-aged obese adults who were randomly assigned to either a low-fat or a low-carb diet.
People in the low-carb group followed an Atkins-style plan, strictly limiting carbohydrates to 20 grams for the first 12 weeks with vegetables as the only source. After Phase I, they gradually added small amounts of carbs from fruit, grains, and dairy foods. They were allowed unlimited fat and protein.
People in the low-fat group consumed between 1200 and 1800 calories per day and aimed for a balance of 55% carbohydrate, 15% protein, and 30% fat.
Both groups were instructed to exercise regularly, mostly by brisk walking. They also were counseled in positive lifestyle habits such as setting reasonable short-term goals and keeping a food diary.
Overall, during the first year, participants lost 11% of body weight, or an average of 22 pounds. The entire group was successful in maintaining about a 15 pound weight loss into the second year. There was no significant difference between the low fat and the low carb groups.
Low Carb May Have Slight Advantage in Cholesterol Readings
However, the researchers did find a difference in cholesterol levels between the two groups. Those on the low fat diet were able to lower LDL cholesterol by about 10mg/dL. For the low-carb dieters, LDL initially increased, but by year two, both groups had LDL levels several points lower than their starting numbers.
Both groups had positive changes in HDL cholesterol as well. Those eating the low-carb diet sshowed an increase of 8 mg/dL. Those in the low-fat group also had an increase in HDL, but not quite as much – 5 mg/dL.
Triglyceride level changes were similar in both groups with low-carb dieters having a slight advantage. Sugar and refined carbohydrates are often factors in high triglyceride levels.
The low-carb dieters also had a greater improvement to diastolic blood pressure than those in the low-fat group. Atkins followers had a three-point decline by year two, versus half of a point for the lower fat group. (Remember that neither diet took sodium into account.)
Unfortunately, those in the low-carb group did report a greater number of side effects from the diet. At the six-month mark 45% reported hair loss and two-thirds had problems with bad breath (likely due to ketosis). After two years, the only side effect that persisted was constipation, occurring in 39% of those on a low carb diet, likely due to a lack of fiber.
Based on this research, either diet can work for both weight loss and reduced risk for certain heart disease factors as long as it is accompanied by other positive health aspects, such as exercise. The key to successful long-term weight loss is to find a diet that you can follow for a lifetime. "In general, dieters should be less concerned about what diet they're on and more focused on finding strategies to stick to the diet they chose," advised Foster.
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This article (also in the Annals of Internal Medicine) offers an alternate view of low-carb vs low-fat diets.
Foster GD, et al "Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet: A randomized trial" Ann Intern Med 2010; 153: 147-157.