Weighing the Evidence on 6 Popular Diet Programs

January W. Payne

About 67 percent of U.S. adults age 20 or older are overweight or obese, according to the National Center for Health Statistics. So many bulging waistlines means quite a market for creators of diet plans. How do you decide which diet plan to try?

To help you evaluate the options, we've compiled information on six popular diet plans that have been studied sufficiently to assess their effectiveness, according to an analysis by Consumer Reports, which weighs in on the topic every few years. (The last CR update was issued in 2007, and the magazine plans to revisit diet plans in 2011.) One tip: Don't repeat a diet program that hasn't worked for you in the past.

"Any diet that gets repeat customers is probably not effective," says James Hill, director of the Center for Human Nutrition at the University of Colorado-Denver.

Whichever diet plan you choose, be aware that you'll need to make a lifestyle change that continues after the program if maintaining weight loss is the goal.

Experts say: "You're not likely going to keep the weight off just by following any of these diets," Hill says. "You need a different long-term strategy that has to include physical activity."

VOLUMETRICS

Description: Based on the book "Volumetrics: Feel Full on Fewer Calories," by Barbara J. Rolls (HarperCollins, 1999), the Volumetrics diet encourages eating low-density foods--choices that are low in calories but high in volume--to help you feel full and satisfied while losing weight. Participants are taught which foods work best (or don't work at all) in a low-calorie diet, and the book provides a menu and exercise plan, too. Favored foods under the plan: beans, fruit, low-fat fish, lean meat, low-fat milk and other dairy items, skinless poultry, and whole grains. Foods to avoid: candy, cookies, and high-sugar drinks.

Studies show: Research shows this diet offered the best shot at weight loss of all the diets for which Consumer Reports most recently evaluated scientific evidence. It earned high marks for short-term and one-year weight loss, and the magazine gave Volumetrics its highest rating for "nutrition analysis"--a measure of how well the diet stacks up against the U.S. Dietary Guidelines for Americans.

Experts say: This diet "makes a good deal of sense scientifically," says Lawrence Cheskin, director of the Johns Hopkins Weight Management Center, Baltimore, Maryland. "What actually stops our eating too much is that we feel that we're filled up." Salads, for example, are desirable, as are any foods that have high fiber and water content levels because they "make you feel fuller with less calories."

WEIGHT WATCHERS

Description: This weight-management program, more than 40 years old and known for its weigh-ins and weekly meetings, is based on four "pillars": healthy weight loss (up to 2 pounds a week and possibly more after the first three weeks), a plan that fits into your life (by including the flexibility to eat any foods you like as long as the points assigned to each add up to no more than your daily target), the ability to make informed choices (by explaining why certain choices are important), and finally, a holistic view that incorporates behavior (by teaching you how to deal with hunger and handle temptation), exercise, food, and support.

Studies show: Participating in Weight Watchers produces average weight loss in the short term, according to Consumer Reports, and participants seem to be able to adhere to the plan over the long term. It also earned CR's highest mark for nutrition analysis.

Experts say: Weight Watchers is a "reasonable, sensible diet," Cheskin says. Hill agrees that the diet can result in health-improving weight loss but notes that you may grow weary of taking part in the Weight Watchers activities. "Even successful people get tired of going to groups," he says. (You can also sign on for the do-it-yourself version of the program online.)

JENNY CRAIG

Description: The program involves making lifestyle changes that incorporate three areas: a healthy relationship with food, physical activity, and balance and motivation in your life as a whole. Participants can sign up in person, by phone, or online; prepared meals and snacks are the core of the program.

Participants are given a customized plan built for them with the assistance of a "personal consultant" who coaches clients through their weight loss, as well as three meals and up to three snacks per day to be accompanied by fresh fruits and vegetables. The company says its meals teach clients about eating a nutritious, balanced diet that is high in fiber and moderate in fat and sodium.

Studies show: People who stick with the Jenny Craig plan lose considerable weight, according to Consumer Reports, but a study involving Jenny Craig client histories showed a high dropout rate. A clinical trial that followed program participants had better results.

Experts say: Since long-term data are hard to come by, it's unclear whether Jenny Craig participants are able to keep the weight off over the long term, Hill says. Participants "lose weight (and) look great" but need to make lifestyle changes to keep the weight off down the line.

E-DIETS

Description: An online, subscription-based service, eDiets was started in 1998. The program, which includes home delivery of balanced meals, snacks, and desserts, offers 20 diet plans (customizable based on foods you enjoy), and the website offers members-only access to menus, recipes, support groups, and diet experts.

Studies show: Adherence to the plan earned average marks from Consumer Reports, and weight loss was found to be below average. eDiets earned high marks in the magazine's nutrition analysis category.

"The data that I've seen shows it really produces fairly minimal weight loss," Hill says. "But is that a bad thing if it takes little effort and you get a little bit of weight loss?"

ORNISH DIET

Description: Based on the book "Eat More, Weigh Less: Dr. Dean Ornish's Life Choice Program for Losing Weight Safely While Eating Abundantly," by cardiologist Dean Ornish (Harper Paperbacks, 2000), the idea is that what you eat matters more than how much you eat. The book includes 250 low-fat recipes that, according to Ornish, cannot only help you lose weight but also lower cholesterol and decrease the risk of heart disease and other illnesses. The caveat? Adopting this diet means no alcohol, fish, meat, oils, sugar, or white flour.

Studies show: Weight loss over the long term is average, according to Consumer Reports, but long-term adherence is below average. It also earned an average mark on the nutrition analysis scale.

Experts say: Hill says he likes the Ornish diet because it's low in fat. "But the problem is it's so low in fat that it's hard for people to stick with it," he says. "It's effective but maybe not practical." The plan also emphasizes physical activity, which is a "shortcoming of other diet plans," Hill says.

ATKINS DIET

Description: This well-known high-protein, low-carb diet was first described in the book "Dr. Atkins' Diet Revolution" (Bantam, 1981). The diet is based on the concept that by eating fewer carb-containing foods and instead predominantly consuming protein plus vegetables with lots of fiber, your body burns fat rather than carbs as its main source of fuel. The first phase of the program mostly bans carbs, though later it gets a little less restrictive. ("The New Atkins for a New You: The Ultimate Diet for Shedding Weight and Feeling Great"; Fireside, March 2010, adds the latest information about the Atkins diet, such as a new requirement for at least five servings of high-fiber vegetables and advice about how to get rid of symptoms that may occur when switching to a low-carb diet.)

Studies show: Long-term adherence to the Atkins diet is below average because some people find its requirements too restrictive, according to Consumer Reports. Weight loss over the long term is average, and it earned Consumer Reports' poorest rating for nutrition analysis.

Experts say: Atkins is hard to stick with in the long run. The problem is that "people who do it for a long time really start craving carbs, and [Atkins] doesn't encourage a balanced kind of eating," Hill says.

Bottom line for all diets: Research shows that "it doesn't matter what kind of diet you're doing as much as it matters your adherence to the diet and your willingness to make dietary changes," Cheskin says. One day, scientists hope to develop a way to prescribe diets based on a person's metabolism, health risks, and dietary preferences. That may mean, for example, "if you're prone to diabetes, maybe a low-fat, low-carb diet" that works for you individually, Cheskin says. "We're in the infancy of really understanding which diets are better for which people."

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Health & Fitness - Weighing the Evidence on 6 Popular Diet Programs