For the 70% of American adults that are overweight or obese, jumping on the popular-diet bandwagon may seem like the answer to their lose-weight-fast conundrum. However, an analysis of clinical trials on four popular diets proves inconclusive regarding their long-term benefits.

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Atkins, South Beach, Weight Watchers and Zone diets are popular for weight loss, but how do they rate in the long term?

The Atkins, South Beach, Weight Watchers and Zone diets are rumored to be the go-to diets for healthy-living gurus and celebrities, with the likes of Kim Kardashian, Jennifer Aniston, Brad Pitt and even Bill and Hillary Clinton joining the latest food fads.

These popular commercial diets have been proven effective in assisting weight loss in the short term. However, according to a study published in Circulation: Cardiovascular Quality and Outcomes, an American Heart Association journal, long-term outcomes of weight loss and impacts on heart health are unclear.

With such a high percentage of the US population recognized as overweight or obese, associated risk of health problems such as heart disease, stroke, high blood pressure and diabetes soars. Hence, whether a diet will be effective to combat those risks in the long term becomes an important public health question.

Dr. Mark J. Eisenberg, the study’s senior author and professor of Medicine at Jewish General Hospital/McGill University in Montreal, Canada, says:

Despite their popularity and important contributions to the multimillion dollar weight loss industry, we still do not know if these diets are effective to help people lose weight and decrease their risk factors for heart disease.”

“With such a small number of trials looking at each diet and their somewhat conflicting results, there is only modest evidence that using these diets is beneficial in the long term,” he continues.

Researchers analyzed clinical trials on four popular diet plans – Atkins, South Beach, Weight Watchers and Zone – in addition to “usual care.” Usual care refers to traditional methods to promote weight loss, such as low-fat diets, behavioral weight loss intervention, nutritional counseling or self-help materials.

When comparing the Atkins, South Beach, Weight Watchers and Zone diets with usual care in clinical trials, the study finds:

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Being overweight or obese increases cardiovascular risk factors.
Image credit: American Heart Association
  • Weight Watchers: dieters lost an average 7.7-13.2 pounds after 1 year and partially regained lost weight after 2 years
  • Atkins: findings were inconsistent across trials
  • South Beach: no comparable difference with usual care in weight loss occurred in 1 year, although participants in this study were both severely obese and had undergone gastric bypass surgery
  • Usual care: dieters lost an average 1.8-11.9 pounds.

Longer-term studies over 2 years have examined both the Atkins and Weight Watchers diets, finding dieters to have partially regained their lost weight over the duration of the study.

Head-to-head comparisons

In head-to-head trial comparisons, Atkins, Weight Watchers, Zone and usual care resulted in modest weight loss at 1 year. Weight loss averages for each diet consisted of:

  • Atkins – 4.6-10.3 pounds
  • Weight Watchers – 6.6 pounds
  • Zone – 3.5-7 pounds
  • Usual care – 4.85 pounds.

In another head-to-head comparison, the team observed no marked differences between Atkins, Weight Watchers, and Zone diets at improving cholesterol, blood pressure, blood sugar levels or other cardiovascular risk factors.

The researchers highlight the need for large clinical trials to be conducted to compare all four popular diets in terms of weight loss and impact on risk factors for health problems such as heart disease. Dr. Eisenberg comments:

A broader lifestyle intervention, which also involves doctors and other health professionals, may be more effective.”

“This also tells doctors that popular diets on their own may not be the solution to help their patients lose weight,” he adds.

Researchers conclude there is insufficient and conflicting data to determine if one of these popular diets is more beneficial for weight loss and heart health.

Medical News Today recently reported on a study finding that consuming a Mediterranean diet with nuts and extra-virgin olive oil may reverse metabolic syndrome.