If the bathroom scales reproach you with their tale of Christmas excess, here is a piece of advice: do not waste time trying to decide which diet to follow.
A comparison of four popular diet plans, including Weightwatchers and Atkins, has shown that it is not the diet you choose that determines how much weight you lose, but the rigour with which you follow it.
Any diet will do so long as you stick to it, researchers have found. Low carb or no carb, high or low fat, protein rich or poor - it makes no difference.
The finding suggests scientists may have to change their approach to the treatment of obesity. Instead of searching for the most effective diet, they should be matching individuals to the diets that best suit them.
This new science, dubbed "nutrigenomics", could increase adherence rates among dieters and promote weight loss, they say. But there is currently no way for doctors to match a diet to an individual's "diet response genotype", the genetically determined way in which they react to certain foods.
It has always been known that success in dieting depends on the dieter's determination to change. But the new research suggests that if a way could be found for individuals to select the right diet for them, it could ease the demands on will power.
The finding comes as the dieting and fitness industries enter their peak January season, when millions of people seek to repair the damage caused by the festivities. But the evidence suggests that up to half will fail. The researchers found that between 35 and 50 percent of those who started the four diets had abandoned them within a year.
In the study, Michael Dansinger and colleagues from the Tufts-New England Medical Centre in Boston, US assessed adherence rates and the effectiveness of four popular diets - Weightwatchers (restriction of portion sizes and calories), Atkins (minimise carbohydrate intake without restriction of fat), Zone (moderate macronutrient balance and glycemic load) and Ornish (restrict fat).
They followed 160 overweight adults aged 22 to 72 who had high blood pressure, high cholesterol, high blood sugar or other health problems who were randomly assigned to one of the four diets.
The results showed that average weight loss after a year was 2kg for Atkins (53 percent completed); 3kg for Weightwatchers (65 percent completed); 3,2kg for Zone and 3,3kg for Ornish (50 percent completed).
"All four diets resulted in modest statistically significant weight loss at one year with no statistically significant differences between diets," the authors write.
"We found that a variety of popular diets can reduce weight... but only for the minority of individuals who can sustain a high dietary adherence level."
The Atkins diet has developed into a worldwide phenomenon with tens of millions of adherents, despite running counter to orthodox medical advice. Some doctors have warned that the high protein regime could do damage.
Robert Eckel of the University of Colorado argues for individualised diets. "It seems plausible that for the maintenance of reduced body mass, the right diet needs to be matched with the right patient. At present, there are no data to help clinicians practicably match a diet to an individual patient's diet response genotype."
He offers a simple answer to those seeking guidance on popular diets. In the absence of conclusive evidence, the best way to lose weight is to reduce calories and increase exercise, he says. - The Independent