Study: Little Proof for Weight Loss Claims

Jan. 2, 2005 — -- In a surprising look at 10 of the most popular diet plans, including Jenny Craig, Optifast and others, scientists say that there is not enough evidence to support most of their claims that they help people lose weight and keep it off.

Only Weight Watchers -- the old stand-by program of point counting, exercise and group meetings -- shows any significance in helping people shed pounds and keep them off, according to a study being published Monday in The Annals of Internal Medicine.

Nutrition expert Dr. David Katz told "Good Morning America" that investigators looked for all of the medical studies they could find to back up the claims of the commercial weight-loss program and found only one scientifically solid article, which showed some evidence supporting Weight Watchers.

"I don't think the findings will surprise the professional community, but I think they'llshock the country," said Katz.

Even the Weight Watchers program did not offer significant, sustained weight loss, said Katz. After two years, participants sustained a modest loss of about 3 percent of their body weight.

Katz added, though, that the study does not definitively say the other programs don't work, but that people have to be wary of the marketing claims of these diets.

"The important thing to note about the others is absence of evidence is not the same as evidence of absence," he said. "We don't know that these programs don't work.The public should know that the marketing hype offers absolutely no proof."

Weight Watchers wins because it guides people toward healthier lifestyle choices over the long term, said Katz.

Katz said that when considering any weight loss program, people should consider three factors -- permanence, family and readiness.

"Permanence means will I learn something or acquire a skill I can use forever? If it's about a short-term program, you get on, you get off, you lose weight, and in awhile it'll come back on," said Katz.

The program also has to take family members into consideration, he said, because it's difficult to stick with a program that doesn't include the rest of your household.

But perhaps most important, the dieter has to be ready to make the commitment to a program. "There's nothing a program can do for you that you're not willing to do for yourself," said Katz. "So assess your readiness. Ask about the pros and cons of change. … Do I really want to make a lasting lifestyle change?"

To see the study when it is published, visit The Annals of Internal Medicine Web site at www.annals.org.