WASHINGTON Looking for that perfect diet? Researchers have bad news -- all diets have just about the same result, and none of them are great, U.S. researchers reported on Monday.
A typical diet helps people lose an average of 6 percent of their weight, typically 10 to 15 pounds (5 to 7 kg), and most people put it all back on after five years.
Weight loss drugs are similarly ineffective in the long run, said Dr. Michael Dansinger of the Tufts-New England Medical Center in Boston.
"It's disappointing but I am optimistic that we can do better in the future. We are learning some of the factors that improve the effectiveness (of diets)," said Dansinger, whose study is published in the Annals of Internal Medicine.
The news is bad for those who hoped a gentler approach to dieting might be more effective over the long-term. Programs that made people eat fewer calories worked better, as did those that involved more frequent visits to either diet groups or to a counselor's office.
But there is good news -- even a small, temporary weight loss can benefit health, Dansinger said.
"A modest weight loss of six percent that is partially maintained for five years is likely to have important health benefits such as delaying the onset of diabetes," he said in a telephone interview.
Dansinger and colleagues looked at the results of 46 trials that included nearly 12,000 people.
About half were on diets. Dansinger said it was difficult to find good studies that included a control group not on a diet. It was also hard to find studies that followed people for more than three years.
The only commercial program included in the study was Weight Watchers. Most were government or university-sponsored programs.
No studies that included food or shakes were included because they did not include a non-dieting group for comparison.
"The results we found, 6 percent weight loss after one year, is in the same ballpark as most of the studies of weight loss, including studies of weight loss medications," Dansinger said.
"We also found the weight loss gradually goes away so that about half the weight loss was gone within three years and almost all the weight loss was gone within five years. That that is also similar to what has been found with weight loss medications."
Dansinger said some of the studies included exercise, but his analysis was not designed to tell whether exercise helped weight loss last longer.
Nearly two-thirds of U.S. adults are overweight or obese, with a higher risk of diabetes, heart disease, high blood pressure, arthritis and cancer.