Weight loss programs: Volumetrics, Weight Watchers

About 67 percent of U.S. adults ages 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 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.

ONE TIP: Don't repeat a diet program that hasn't worked for you in the past.

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. It will have to include physical activity.

VOLUMETRICS

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 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.

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.

WEIGHT WATCHERS

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.

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 nutritional analysis.