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NEW YORK (Reuters Health) - People who take part in a commercial weight-loss program may indeed shed some pounds - especially if they substantially cut calories, a new study from Sweden finds.
Worldwide, around 1.5 billion adults are overweight and another half billion are obese. In the U.S., two-thirds of adults are overweight or obese. That's a huge market for commercial weight-loss programs, but few studies have looked at whether they really work.
The popular Weight Watchers and Jenny Craig programs are among the few that have been tested in clinical trials, with promising results: People in the programs lost more weight over two years than people assigned to "usual care" - generally advice from a doctor or dietitian. (See Reuters stories of September 8, 2011 and November 4, 2011).
The newest study followed over 9,000 adults who enrolled themselves in Itrim, a popular chain of weight-loss and exercise centers in Sweden. The company just recently expanded to the U.S., opening a center in San Francisco .
Over a year, program clients lost an average of 11 to 25 pounds, depending on how strict they were willing to get with calories.
On the other hand, up to one-quarter dropped out, according to results published in the American Journal of Clinical Nutrition.
The Itrim program is different from its better-known competitors, according to Erik Hemmingsson, a researcher at the Karolinska Institute in Stockholm who led the study.
Weight Watchers promotes eating "normal food" and trimming calories, while Jenny Craig typically provides prepackaged lower-calorie meals, then has people gradually go back to regular meals.
People in the Itrim program choose an eating plan, with the help of a "health coach," and take up an exercise regimen. The strictest diet plan involves downing liquid meals of just 500 calories a day for six to 10 weeks, then gradually reintroducing normal food.
If that sounds too daunting, people can combine liquid meals and lower-calorie regular meals for a total of 1,200 to 1,500 calories per day, or stick with normal food but trim calories to 1,500 to 1,800 per day.
In their study, Hemmingsson and his colleagues found that the strictest diet worked best. Among nearly 3,800 clients who chose it, the average weight loss over one year was 25 pounds.
Almost 4,600 people who opted for the liquid meal/real food combo came in second. They shed 15 pounds, on average. Meanwhile, the group that stuck with normal food - 676 clients in all - trimmed an average of 11 pounds.
It remains to be seen how widely appealing the program could become, according to Hemmingsson, who was once employed by Itrim and has received consultancy fees from the company. (Itrim also funded the current study.)
This study was not a clinical trial, wherein people were randomly assigned to the Itrim program or to routine healthcare: Everyone in the study chose to enroll, put their own money up and were motivated to shed pounds.
Even so, clients dropped out: anywhere from 18 percent to 26 percent, depending on the plan. (The strictest, liquid-meal plan had the lowest dropout rate.)
And of course, they paid a price. The cost of Itrim over one year, excluding the liquid meals, is equivalent to $1,300.
But the findings do underscore the importance of old-fashioned calorie-cutting, Hemmingsson said.
"Calories are still what counts and makes a difference regardless of the setting - clinical or commercial," Hemmingsson said.
Yet that simple principle - burn more calories than you take in - is often forgotten when people try to shed weight, he noted. "It's not rocket science, but it works," Hemmingsson said.
Commercial diet programs might help when people have trouble making those changes themselves, or staying motivated over time, according to Hemmingsson.
He said he thinks the support in the Itrim program is "absolutely crucial."
When people enter the program, they discuss their diet strategy with a health coach. And after the first three months - the "weight loss phase" - they start going to their local Itrim center for a workout two or three times a week. They also continue to get diet and lifestyle advice.
Researchers still have a lot to learn about commercial weight loss programs, including whether people maintain their initial success over the long haul.
"We generally need to raise the bar by designing studies with a much longer follow-up, say three to five years," Hemmingsson said.
For now, he suggested that people zero in on calories if they want to win the battle of the bulge.
"If you are serious about losing weight," Hemmingsson said, "then you should focus on calorie cutting - for example, by using meal replacements - and adopt a more physically active lifestyle."
If that's too difficult on your own, he added, a commercial program might help. But he advised choosing one that has actually been held up to some scientific scrutiny.
SOURCE: American Journal of Clinical Nutrition, online September 18, 2012.