Study Compares Year-long Effectiveness of Four Weight-loss Plans
The very low carbohydrate diet known as the Atkins diet may contribute to greater weight loss than higher carbohydrate plans without negative effects such as increased cholesterol. Christopher Gardner, Ph.D., and colleagues at Stanford University conducted an NCCAM-funded study of 311 pre-menopausal women, all of whom were overweight or obese. Each woman was randomly assigned to one of four diets. Each of the diets used were selected for their different levels of carbohydrate consumption:
- The Atkins diet is very low in carbohydrate consumption: less than 20 grams of carbohydrates per day and increasing to 50 grams per day.
- The Zone diet is designed so that a person's daily calorie consumption is comprised of 40 percent carbohydrates, 30 percent protein, and 30 percent fat.
- The LEARN diet (Lifestyle, Exercise, Attitudes, Relationships, and Nutrition) instructs participants to get 55 to 60 percent of their calories from carbohydrates, and not more than 10 percent from saturated fat. This diet is based on the USDA food pyramid.
- The Ornish diet's primary guideline states that participants should not get more than 10 percent of their calories from fat.
Participants in each group received books that accompanied their assigned diet plan, and attended hour-long classes with a registered dietitian once a week for the first 8 weeks. Data on the participants was collected at the beginning of the study, and at 2, 6, and 12 months. The researchers recorded body mass index (BMI); percent body fat; waist-hip ratio; as well as metabolic measures such as, insulin, cholesterol, glucose, triglyceride, and blood pressure levels.
The Atkins diet group reported the most weight loss at 12 months with an average loss of 4.7 kilograms, or just over 10 pounds. They also had more favorable overall metabolic effects. Average weight loss across all four groups ranged from 3.5 to 10.4 pounds. The authors note that “even modest reductions in excess weight have clinically significant effects on risk factors such as triglycerides and blood pressure.”
Gardner CD, Kiazand A, Alhassan S, et al. Comparison of the Atkins, Zone, Ornish, and LEARN Diets for change in weight and related risk factors among overweight premenopausal women. The A to Z Weight Loss Study: a randomized trial. Journal of the American Medical Association.; 297(9):969–977.2007