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Weight Loss Success -- The Most Important Determinant

By Michael Smith, MD

Adherence to diet for one year, not the specific diet plan, is the most important determinant of successful weight loss. According to the results of a randomized trial published in the January 2005 issue of JAMA. When comparing Atkins, Ornish, Weight Watchers, and Zone diets, the author recommends the "low fad" approach.

The Low Fad Approach

Successful weight loss is best achieved by following the low fad approach. The low fad approach to losing weight involves moderate reductions in caloric intake with increased physical activity. There is nothing "fad" about this approach and is supported by a few studies.

The fact that the low fad approach is backed by scientific evidence is key...the fad diets currently in the market have very little credible evidence supporting their claims.

"The scarcity of data addressing the health effects of popular diets is an important public health concern, especially since patients and physicians are interested in using popular diets as individualized eating strategies for disease prevention," write Michael L. Dansinger, MD, a Preventative Medicine specialist from Boston, Massachusetts.

Dr. Dansinger goes on to say, "Some plans minimize carbohydrate intake without fat restriction (eg, Atkins diet), many modulate macronutrient balance and glycemic load (eg, Zone diet), and others restrict fat (eg, Ornish diet)."

So, besides the lack of evidence backing the claims made by fad diets, there is no consistency from one diet to the next within the same category of diet type. This makes it extremely difficult to study the fad diets and measure the effects on your health, let alone your chances for successful weight loss.

But there's hope for dieters...the low fad approach or "Low Fad Diets."

Successful Weight Loss...The Evidence Supporting Low Fad Diets

At a single academic medical center, 160 overweight or obese adults were randomized to the Atkins, Zone, Weight Watchers (calorie restriction), or Ornish diet. The total time of the study was one year. The age range was 22 to 72 years, mean body mass index (BMI) was 35 kg/m2 (range, 27-42 kg/m2), and all participants had high blood pressure, high cholesterol, or diabetes.

After two months of maximum effort, participants controlled their degree of adherence to the diet. Primary outcomes were changes in baseline weight and cardiac risk factors at one year, and dietary adherence rates based on self-report.

The percent of subjects who were able to finish the study and stick with their diets for one year were 53% for Atkins, 65% for The Zone, 65% for Weight Watchers, and 50% for Ornish. Participants who discontinued the study were assumed to have no change from baseline in their weight.

At one year, mean weight loss was 6-7 pounds for Atkins, 6-9 pounds for The Zone, 6-8 pounds for Weight Watchers, and 6-10 pounds for The Ornish Diet.

Compared to subjects that quit the study before one year, the subjects that made it to one year experienced greater weight loss. In each group, approximately 25% of the initial participants maintained a one-year weight reduction of more than 5% of initial body weight, and approximately 10% of participants lost more than 10% of body weight.

The amount of weight loss was associated with the self-reported level of dietary adherence. Basically, the longer a subject stayed on the diet that they were randomized to, the more weight loss they experienced. However, the type of diet they were on had no real effect on the amount of weight loss. The type of diet also had no effect on dropping their blood pressure or lowering their cholesterol level.

Successful Weight Loss Conclusion

The author concluded, "Each popular diet modestly reduced body weight and several cardiac risk factors at one year." Overall, dietary adherence rates were low, although increased adherence was associated with greater weight loss and cardiac risk factor reductions for each diet group.

The study limitations include the inability to identify a "best diet" and the limited ability to exclude long-term safety risks.

Lastly, the author stated, "One way to improve dietary adherence rates may be to use a broad spectrum of diet options, to better match individual food preferences, lifestyles, and cardiovascular risk profiles." I have always supported the idea of more personalized weight loss plans.

The General Clinical Research Center via the National Center for Research Resources of the National Institutes of Health, the U.S. Department of Agriculture, and the Boston Obesity Nutrition Research Center supported this study on successful weight loss.

To Healthy Living!

Michael A. Smith, MD
Chief Medical Consultant
Diet Basics Website

The complete study can be found at JAMA. 2005;293:43-53, 96-97.

Dr. Smith is the Chief Medical Consultant for Diet Basics, a content rich weight loss web site. He is dedicated to the education of all dieters. Please visit his site at Diet Basics.