Weight Loss Diets Promote Heart Health
Several different popular diets may be helpful for losing weight and may reduce some heart disease risk factors, reports the Journal of the American Medical Association (2005;293:43–53). The new study compared the effects of the Atkins, Ornish, Weight Watchers, and Zone diets over the period of one year.
About 50% of Americans are considered overweight or obese, increasing their chances of developing heart disease, high blood pressure, diabetes, stroke, gallbladder disease, osteoarthritis, and some types of cancer. Several types of diets have been developed to help people lose weight, and while the promoters of many of these popular diets promise rapid weight loss, relatively little is actually known about their safety and efficacy.
The recommended proportions of fat, protein, and carbohydrates among different weight-loss diets range widely. Those diets that restrict total caloric intake and moderate fat intake (20 to 30% of total calories) are the most widely recommended by healthcare professionals. Weight Watchers is an example of this type of diet. The Atkins diet, on the other hand, does not limit calories but instead emphasizes carbohydrate restriction with most calories coming from fat and protein. The Zone diet is also a low-carbohydrate diet that emphasizes eating carbohydrates, fat, and protein in a ratio of 40:30:30. The Ornish diet is a vegetarian diet with less than 10% of the total calories coming from fat.
The new study examined the effects of the Atkins, Zone, Weight Watchers, and Ornish diets on weight loss and cardiovascular disease risk factors in 160 overweight and obese people. The participants were 22 to 72 years old, and had one or more risk factors for heart disease, including high blood pressure, elevated blood fats (triglycerides, total cholesterol, LDL [“bad”] cholesterol), low HDL cholesterol (higher levels of HDL are protective against heart disease), or high blood sugar. Each of the participants was assigned to follow one of the four weight-loss diets to the best of their ability for two months, and then according to their own level of interest for an additional ten months.
Participants in the Atkins group were instructed to consume less than 20 grams of carbohydrates per day, gradually increasing to 50 grams per day. The Zone diet group was to keep the percentage of calories from carbohydrates, fat, and protein in a ratio of 40:30:30. The Weight Watchers group was encouraged to keep the daily “points” between 24 and 32 (each point is approximately 50 calories). Participants in the Ornish group ate a very-low-fat vegetarian diet. The following measures were taken at the beginning of the study, and again at 2, 6, and 12 months: weight, blood fats, blood sugar, blood pressure, C-reactive protein (a marker of inflammation in the body; higher levels are associated with increased risk of cardiovascular disease), and self-reported dietary adherence.
Each diet type led to significant weight loss after one year. The amount of weight loss did not differ between groups, but instead was associated with how closely the participants followed the diet. All four diets decreased the ratio of LDL to HDL cholesterol by 10%, suggesting a reduction in heart disease risk. Each diet also decreased LDL cholesterol, and C-reactive protein levels dropped by 15 to 20% in each group. There were no significant changes in blood pressure, triglycerides, or blood sugar in any diet group after one year.
The results of this study indicate that each of these diets can decrease weight and reduce the risk of heart disease when closely followed. For each diet, cardiac risk factors decreased proportionately with the amount of weight lost, suggesting that weight loss but not diet type predicts a decrease in cardiovascular disease risk.
Kimberly Beauchamp, ND, received her bachelor’s degree from the University of Rhode Island and her Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. She is a co-founder and practicing physician at South County Naturopaths, Inc., in Wakefield, RI. Dr. Beauchamp teaches holistic medicine classes and provides consultations focusing on detoxification and whole-foods nutrition.
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