Popular diet plans lack evidence for long-term benefits

While popular diet plans such as Atkins could help people lose weight in the short term, the long-term benefits of such plans have been questioned by a team of researchers. Writing in the journal Circulation: Cardiovascular Quality and Outcomes, the Canadian led team analysed and compared the results of randomised clinical trials on four popular commercial diet plans - South Beach, Weight Watchers, Zone and Atkins. Led by senior author Professor Mark Eisenberg, the team found that the four plans were all ‘modestly efficacious’ at decreasing weight in the short term - but that these benefits are not sustained long-term. "Despite their popularity and important contributions to the multi-million 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," commented Eisenberg. "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 said. Study details The team identified 12 randomised controlled trials (RCTs) published in English with follow-up of greater than 12 months, ten of which tested one of the four diets against ‘usual care’ while two were ‘head to head’ RCTs comparing two of the diets against a control. According to their analysis, the team found that at 12 months, the 10 RCTs comparing popular diets to usual care revealed that only Weight Watchers (WW) was consistently more efficacious at reducing weight. Indeed, in trials comparing Weight Watchers to usual care, Weight Watchers dieters lost an average 7.7 to 13.2 pounds after one year compared to 1.8 to 11.9 pounds with usual care, however at 2 years, the weight lost was partially regained. “However, the 2 head-to-head RCTs suggest that Atkins, WW, Zone, and control all achieved modest long-term weight loss,” said the team. Trials involving head-to-head comparisons between Atkins, Weight Watchers, Zone and usual care suggested that all four result in a modest weight loss at one year, as did those in the control group who received the usual care, they confirmed. According to the analysis, those on the Atkins diet lost an average 4.6 to 10.3 pounds; Weight Watchers participants lost an average 6.6 pounds; Zone dieters lost an average 3.5 to 7 pounds; and control lost about 4.85 pounds. Eisenberg and his colleagues also noted that studies involving head-to-head comparisons showed that there were no marked differences between Atkins, Weight Watchers, and Zone diets at improving cholesterol, blood pressure, blood sugar levels, or other cardiovascular risk factors. Furthermore, data for 24 months suggests that weight lost with Atkins or WW is partially regained over time. “Our results suggest that all 4 diets are modestly efficacious at decreasing weight in the short term, but that these benefits are not sustained long-term,” the authors concluded. Source: Circulation: Cardiovascular Quality and Outcomes Published online ahead of print, doi: 10.1161/CIRCOUTCOMES.113.000723 “Long-Term Effects of 4 Popular Diets on Weight Loss and Cardiovascular Risk Factors. A Systematic Review of Randomized Controlled Trials” Authors: Renée Atallah, Kristian B. Filion, et al

Popular diet plans lack evidence for long-term benefits

Popular commercial diets can aid weight loss in the short term, but the long-term impacts on weight maintenance and heart health remain ‘unclear’, say researchers.

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