Adherence, not diet type, the key to trimming the fat

Shelley Wood

January 06, 2005

Jan 6, 2005

Chicago, IL - Depending on how it's looked at, a new study may fuel or thwart the New Year's resolutions of men and women hoping to lose weight over the coming year. Researchers writing in the January 5, 2005 issue of the Journal of the American Medical Association say that the type of diet followed is less important than actually adhering to a diet in the long term [ 1 ]. The findings held not only for weight loss in obese or overweight participants but also for reduction in cardiac risk factors over 1 year.

"In the long run," they write, "sustained adherence to a diet rather than diet type was the key predictor of weight loss and cardiac-risk-factor reduction in our study."

Dr Michael L Dansinger (Tufts-New England Medical Center, Boston, MA) and colleagues randomized 160 overweight or obese men and women to 1 of 4 popular diets: the Ornish (low-fat), the Atkins (low-carb), the Zone (low-glycemic index), and the Weight-Watchers (portion-/calorie-restricted) diets. For the first 2 months, participants attended a total of 4 "diet classes" to help them adhere to their diet; thereafter, participants were left to adhere to the diets as best they could.

After 1 year, Dansinger et al report modest weight reduction for patients in each of the groups, with no statistically significant differences between the diets (and assuming no change from baseline for people who discontinued the study). Dropout rates were highest for the Atkins and Ornish diets, with roughly half of all dieters in those 2 groups quitting before the year was out.

"The higher discontinuation rates for the Atkins and Ornish diet groups suggest many individuals found these diets to be too extreme," the authors say.

While the diets appeared to have different effects on lipid levels, changes in LDL/HDL ratios were similar between the 4 diets, and specific effects of certain diets on serum triglycerides and blood pressure were not sustained at 1 year, the authors note.

Weight and lipid changes as well as dropout rates over 12 months

Weight Watchers
Weight (kg)
LDL (mg/dL)
HDL (mg/dL)
LDL/HDL ratio
Triglycerides (mg/dL)
Dropout rate (%)

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Dansinger and colleagues say their study underscores the need for better ways of encouraging diet adherence and suggest that different diets may be more appropriate for different people. In their study, people were not permitted to choose their diet; such a strategy may have increased adherence, they propose.

In a press release issued by Tufts-New England Medical Center, Dansinger emphasizes that "there is not 1 diet that fits all, and many great options exist."

"To find the one that's best for you, try 'dating the diets' as if looking for a lifelong partner. You may kiss a few frogs along the way, but once you find the one you can live with forever, stand by your plan."

Time for a low-fad approach?

In an accompanying editorial, Dr Robert Eckel (University of Colorado, Denver) points out that comparative data for the wildly popular diets have "remained elusive" and while Dansinger et al's study "could be the randomized trial many have been waiting for," the results may disappoint, showing no one diet to be better than the others [ 2 ].

What are needed now are studies to determine whether specific weight-loss strategies can be matched with the right patients to optimize results, Eckel says. Also pressing is evidence to prove that weight loss and risk-factor modification by diet and lifestyle changes can be sustained over time and whether these changes can translate into hard clinical outcomes.

The varying effects of low- and high-carbohydrate or low- and high-fat diets on lipids has garnered a lot of attention in conjunction with the rising popularity of low-carb diets. But as Dansinger et al as well as Eckel point out, the ability of low-carb diets to boost HDL but produce minimal or no effects on LDL while low-fat diets' apparent ability to lower LDL but leave HDL levels untouched may have an overall null effect on cardiovascular risk. Indeed, until these sorts of changes are linked to adverse health consequences, focusing too heavily on lipid changes may not be warranted.

Overall, Eckel writes, "physicians and other healthcare professions should teach obese patients that both quality and quantity of the diet are important and that sustained weight loss may well be possible with the addition of physical activity and behavioral change strategies to a modest but persistent caloric restriction—the "low-fad" approach.

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  1. Dansinger ML, Gleason JA, Griffith JL, et al. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA. 2005; 293:43-53.

  2. Eckel RH. The dietary approach to obesity: is it the diet or the disorder? JAMA. 2005; 293:96-97.


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