SATURDAY, Oct. 9 (HealthDay News) -- Two new studies support the notion that structured diet and exercise plans -- and perhaps some free prepared meals -- can help the obese and severely obese lose weight.

Both studies used prepackaged meals in their protocols, with one utilizing the Jenny Craig program. That study was funded by Jenny Craig.

"Physicians should be aware that lifestyle changes actually do work. . . [and] they could refer people to this or another program and be optimistic [that although] this is not a magic bullet, people have to adhere," said Cheryl Rock, lead author of the Jenny Craig study, which appears with the other study in the Oct. 27 issue of the Journal of the American Medical Association. Rock reported being on the Jenny Craig advisory board in 2003 and 2004.

Also encouraging, she added, is the fact that participants had not gained the weight back by the end of two years.

"This shows the promise of lifestyle interventions and I think people [have been] really discouraged," said Marcia G. Ory, director of the Aging and Health Promotion Program at Texas A&M Health Science Center School of Rural Public Health in College Station.

But, she cautioned, "the real question is does it work in the real world and will it sustain, not just in the real world but through a person's life."

Other outside experts also expressed cautionary notes, especially given that such structured plans can not only be difficult to adhere to but also expensive.

"I think we're looking at a best-case scenario," said obesity researcher Rena Wing, author of an editorial accompanying the Jenny Craig article. "Perhaps we need to be studying how to pay for the programs."

"Right now, obesity disproportionately affects lower-income individuals and minorities, and those individuals may not be able to afford commercial programs. So we need to see whether incentivizing or making these programs free would both increase the number of people who participate and lead to good [weight] losses," added Wing, who is a professor of psychiatry and human behavior at the Warren Alpert Medical School of Brown University in Providence, R.I. and has done extensive research on the behavioral treatment of obesity.

In her commentary, Wing also noted previous research suggests that an obese individual enrolling in commercial weight-loss programs will be unlikely to achieve results as favorable as those in the Jenny Craig study.

"I'm skeptical about long-term success when I see programs that provide prepackaged meals," added Keri Gans, a spokeswoman for the American Dietetic Association. "After the program is done, have they actually learned how to prepare these meals again? It doesn't teach you about situations that occur in the real world, for instance, at parties dining out, vacation and on your own. . . [and] for some, financially, this could also be a bit of a strain."

The papers were released early to coincide with presentations slated to be made Saturday at the Obesity Society annual meeting in San Diego.

The first study randomized more than 400 overweight or obese women aged 18 to 69 to receive individualized in-person counseling or weekly telephone counseling as well as free, prepackaged meals and instructions to increase exercise to 30 minutes a day, five days a week, as part of the Jenny Craig program (these participants were later "weaned" off the prepared meals). The control group received two beginning sessions with a dietician plus monthly follow-up contacts.

Jenny Craig participants also received "helpful information such as how to choose from a menu" and eating out was also factored into the program, said Rock, who is a professor of family and preventive medicine at the University of California, San Diego, School of Medicine.

After two years of follow-up, weight loss in the center-based Jenny Craig group was about 16 pounds, or 7.9 percent of the starting body weight. In the telephone-based Jenny Craig group, mean weight loss was almost 14 pounds, or 6.8 percent of body weight, while those in the control group lost only 4.5 pounds, about 2.1 percent of their initial body weight.

Participants received $25 each time they visited the clinic. The normal cost of enrolling in Jenny Craig for a year in the United States is $359. Beyond that, enrollees also have to cover the cost of pre-packaged food, which averaged about $100 a week, but, said Rock, "people would be spending money on food either way."

The second study, led by Bret Goodpaster of the University of Pittsburgh School of Medicine and colleagues, randomized about 100 severely obese people without diabetes, 37 percent of them black, into one of two groups. People in the first group started a diet and exercise plan (also including prepared meals) right away. The second arm was the same, except physical activity started six months after beginning the diet. Both groups had regular contact with a nutritional expert.

After six months, those who had started exercising right at the start had lost more weight (24 pounds) than those who delayed the start (18 pounds). By the end of the year, though, the delayed group was catching up (22 pounds vs. 26 or so pounds in the prepared-meal group).

This represented a clinically significant loss of 8 percent to 10 percent of initial body weight.

Physical exams also showed that blood pressure, insulin resistance, visceral abdominal fat, waist circumference and other warning signs of impending heart disease and diabetes were improved.

Participants were also paid for their involvement in this study and given financial incentives for reaching their behavioral goals, which included brisk walking 60 minutes daily, five days a week, for a target of 10,000 steps a day.

"It's the components that are really important," said Ory. "Maybe to sustain weight loss over time, we're going to have to have the food product along with some counseling, along with physical activity. Any one by itself is not going to be as successful as all the approaches together."

More information

The American Heart Association has more on getting and staying healthy through lifestyle choices.