Popular diets may work for a little while but even the best ones don’t keep most people slim in the long term, doctors reported Tuesday.
Just about everyone starts gaining back weight after a year or so, the researchers report. And it’s not clear what benefits they get for heart health, either.
“Essentially, what they’re telling us is that the diatribe about diets is a bunch of overcooked baloney,” said Dr. David Katz, director of Yale Griffin Preventative Research Center, who wrote an editorial to accompany the study.
"They say, frankly, everyone falls off the wagon at 12 months, to say nothing of 24 months, and are gaining the weight back,” Katz told NBC News.
With more than two-thirds of Americans overweight or obese, it’s an important question. Heart disease and cancer are the top two killers and both are linked with obesity.
Dr. Mark Eisenberg of Jewish General Hospital/McGill University in Montreal, Canada and colleagues reviewed major studies looking at four of the most popular and medically lauded diets: Atkins, South Beach, Weight Watchers, and the Zone.
“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,” Eisenberg said.
“Despite millions of dollars spent on popular commercial diets, data are conflicting and insufficient to identify one popular diet as being more beneficial than the others,” they wrote in the American Heart Association journal Circulation: Cardiovascular Quality and Outcomes.
Their findings: Weight Watchers dieters lost an average of 7.7 to 13.2 pounds after one year while people getting “usual care” such as nutritional counseling lost 1.8 to 11.9 pounds. Weight Watcher dieters gained back at least some pounds after two years.
Head-to-head comparisons of Atkins, Weight Watchers, the Zone and usual care showed people lose a modest amount of weight after a year on all four approaches. Those on the Atkins diet, which stresses eating protein and dumping starchy carbohydrates, 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 those getting counseling lost about 4.85 pounds.
There were no big differences among the diets in terms of improving cholesterol, blood pressure, blood sugar levels, or other heart risk factors. Weight Watchers, which encourages eating plenty of fruits and vegetables and cutting out junk food, seemed to work the best at 12 months, they said.
A similar big study done in 2007 and published in the Annals of Internal Medicine found that a typical diet helps people lose an average of 6 percent of their weight, typically 10 to 15 pounds, and that most people put it all back on after five years.
“Our culture feeds on the marketing hype about the next great fad diet, but when you scratch the surface and look for data there’s just no there there,” said Katz.
But Dr. Barry Sears, who invented the Zone, says weight loss isn’t the point, anyway.
“What you are looking for is health improvement — control of insulin and control of inflammation,” Sears told NBC News.
Sears’s approach aims to reduce inflammation — the process that underlies heart disease and, many scientists believe, Type 2 diabetes. “Studies like this say it doesn’t matter. Well, it does matter,” Sears said. “You need to pick a way of life and stick with it, and a way of life that gives the greatest health for the longest period of time.”
Weight Watchers said studies have shown even a modest weight loss can improve heart risk factors. "Out of 10 randomized clinical trials comparing popular diet books and the Weight Watchers program to usual care, only Weight Watchers was consistently more efficacious at reducing weight," a spokesperson said in a statement.
Linda Van Horn, a nutritionist and professor of preventive medicine at Northwestern Feinberg School of Medicine, said it’s no secret that most people can lose weight initially on a diet, because they eat less for a while.
“It’s more about what diet you’ll stick with, what are you more inclined to adopt and continue in the long term,” Van Horn, an American Heart Association spokesperson who was not involved in the study, told NBC News.
“The popularity of the diet is more about media hype,” she added. “It’s a matter of who can sell more books or what captures the attention of the public.”