How Healthy Are Weight-Loss Diets?
October 25, 2007—The sharp rise in rates of obesity and overweight in the past three decades has generated a thriving weight-loss industry marketing a wide spectrum of diet plans. It is estimated that 50 million Americans embark on weight-loss diets and spend $30 billion for diet programs and products every year, yet little is known about the long-term health effects of different weight-loss programs.
A new study compared the healthfulness of eight popular weight-loss diets—two Weight Watchers plans, Atkins, Ornish, The Zone, South Beach, New Glucose Revolution, and the 2005 US Department of Agriculture Food Guide Pyramid—and gave the best health rating to the Ornish plan: a low-fat, high-fiber, vegetarian diet.
Weight Watchers, the largest commercial weight-loss plan, assigns points to foods based on their fat, calorie, and fiber content. Foods rich in fiber are assigned a lower number than foods high in fat and calories. Dieters aim to keep their points below a specific number determined by their current weight and desired weight loss. Two Weight Watchers plans were included in this study: a high-carbohydrate plan and a high-protein plan.
The Atkins diet is a high-fat, very-low-carbohydrate diet that adjusts carbohydrate allowances over four phases to achieve weight loss and then weight maintenance.
The South Beach diet is a three-phase plan that begins with a reduced-carbohydrate phase and gradually eases to include modest amounts of whole grains.
The Zone diet is a reduced-calorie, reduced-carbohydrate plan that specifies the proportion of daily calories from carbohydrates (40%), protein (30%), and fat (30%).
The Ornish plan, which is vegetarian, emphasizes foods high in fiber and complex carbohydrates, limits fat intake to no more than 10% of a day’s calories, and strictly limits cholesterol and saturated fats.
“Healthy” fats—polyunsaturated and monounsaturated fats from liquid oils, nuts, seeds, avocados, and olives—are recommended in all of these weight loss plans; however, “unhealthy” saturated fats are not restricted in the Atkins plan.
The New Glucose Revolution plan includes a balance of lean protein, healthy fats, and high-fiber complex carbohydrates with a low glycemic index (a measure of how much a food raises blood sugar levels).
The Food Guide Pyramid plan specifies the volume or weight of foods such as fruits, vegetables, whole grains, meats, and low-fat or nonfat dairy products that should be included each day based on scientific information about nutrients and foods that prevent chronic disease and nutrient deficiencies.
The healthfulness of each plan was determined using the Alternate Healthy Eating Index (AHEI), a measure of a diet’s cardiac risk-reducing effects based on several quality assessments: the amount of fruit, vegetable, nut and soy, cereal fiber, the ratio of white to red meat, the ratio of polyunsaturated to saturated fat, and the amount of trans fat (unhealthful partially hydrogenated oils).
The Ornish plan received the best score, followed by the Weight Watchers high-carbohydrate and New Glucose Revolution plans. These plans all received high scores for being high in cereal fiber, vegetables, and fruits, and low in trans fats. The Atkins plan (phase 4, at the lowest recommended level of long-term carbohydrate intake) received the lowest score, having the poorest white-to-red-meat ratio, polyunsaturated-to-saturated-fat ratio, and cereal fiber and trans-fat content.
“Patients and their healthcare providers must be conscious of health concerns when choosing a plan for weight loss because dietary change is meant to be a long-term process,” the study’s authors concluded in the Journal of the American Dietetic Association.
Although most people will achieve short-term weight loss using any of these diets, the researchers point out that long-term weight management and lower heart disease risk are more important. The study’s findings suggest that the weight-loss plans that best address these long-term goals are high in fiber-dense complex carbohydrates.
(J Am Diet Assoc 2007;107:1786–91)
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Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.
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