Researchers analysed critical trials looking at four popular weight loss options: the low-carb Atkins diet; the calorie-counting Weight Watchers plan; the South Beach diet, outlining 'bad' and 'good' carbs and fat; and one which has a 3:4 ratio of protein to carbs known as the Zone diet.
These were compared to more natural ways to lose weight, dubbed 'usual care', such as eating low-fat products, self-help methods and nutritional counselling.
The South Beach diet found no difference in weightloss over 12 months, though those in this group had undergone gastric bypass surgery due to being morbidly obese.
In a trial comparing Atkins, Weight Watchers, Zone and usual care people in all four groups were found to have lost a modest amount in a year. Atkins dieters tended to lose between 4.6 and 10.3lbs; those in the Zone shed 3.5 to 7lbs; while those on Weight Watchers dropped around 6.6lbs; and the control group of usual care around 4.85lbs.
Aspects such as blood pressure, blood sugar levels and cholesterol didn't differ between the different dieters.
However, those who relied on structured plans rather than simply leading a healthy lifestyle were more likely to put on some of the weight shed after two years.
Senior author Dr Mark Eisenberg, Professor of Medicine at Jewish General Hospital/McGill University in Canada, summed up the findings.
"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," he explained.
"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."
To understand the overall benefits Dr Eisenberg added that larger studies needed to be carried out, but he does believe people may just be as well off using traditional weightloss techniques rather than relying on specific diets.
"A broader lifestyle intervention, which also involves doctors and other health professionals, may be more effective," he said.
"This also tells doctors that popular diets on their own may not be the solution to help their patients lose weight."
It's easy to lose weight the natural way if you put your mind to it. Exercising for just ten minutes a day along with leading a balanced diet, sticking to your daily intake of calories (2,000 for woman and 2,500 for men) and having an optimistic attitude all lend themselves well to getting trim.
Findings were published in the journal Circulation: Cardiovascular Quality and Outcomes.
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