Some people who try to "go it alone" wind up abandoning their diets. You've heard of all the plans that can help — here's the skinny on them.

WEIGHT WATCHERS

(800) 651-6000, www.weightwatchers.com

Members: 1.5 million members in 30 countries.

Locations: 48,000 meetings weekly.

Dieting style/method: The science-based weight-loss program includes two food plans, an exercise plan, cognitive behavior skills and group support. Known for "points" system, based on calories, fat and fiber content.

Best fit: Enjoy group support and focused education.

Exercise: Yes. Members can swap activity points for food.

Staff: Meetings are led by trained leaders, all lifetime members of Weight Watchers.

Cost: Registration fee of $15-$20, weekly meeting fee of $9.99-13.99.

Supplements: Available, but not required.

Weigh-ins: Yes.

Background: Based on scientific research, the program is developed by registered dietitians and reviewed by notable Scientific Advisory Board.

Commitment: None. Fees are paid meeting-by-meeting.

Upshot: Extremely effective.

NUTRISYSTEM

(800) 321-8446 (321-THIN), www.nutrisystem.com

Members: 2.7 million members.

Locations: Online or telephone.

Dieting style/method: Portion-controlled, prepared meals. Has 120 different, nutritionally balanced prepared meals (not frozen) delivered to your home. Web site tracks members' weight loss and goals.

Best fit: Busy people who need convenience and don't mind prepared foods.

Exercise: Yes. A free online program called Body Nourish; additional free support is available online or by phone.

Staff: 100 weight-loss counselors with degrees or course work in nutrition, psychology, social work, education and exercise. All counselors receive intensive training.

Cost: The 28-day package costs $289. The plan provides four weeks of meals and snacks. You add your own fruits, vegetables and dairy foods.

Supplements: Yes. Calcium and multivitamins.

Weigh-ins: No.

Background: Dr. Jay Satz and a staff of nutritionists and dietitians. Based on research on the glycemic index, weight control and overall health.

Commitment: A 30-day return policy on unused food.

Upshot: Not the same Nutri-System from many years ago. Much improved, strong program.

JENNY CRAIG

(800) 536-6920, www.jennycraig.com

Members: 100,000 clients.

Locations: 641 centers and online/telephone program.

Dieting style/method: Portion-controlled food and a personalized "food/body/mind approach." Packaged food (70 entrees and snacks) is an additional and required purchase.

Best fit: Busy person, doesn't mind prepared foods and needs focused support.

Exercise: Yes. Counselors create a personal fitness plan.

Staff: Certified by famed Cooper Institute. All employees attend classes in nutrition, exercise, motivation and stress management.

Cost: Six weeks for $36, six months for $199 and one year is $399. Average food cost: $11-$15 per day.

Supplements: Yes. Available at $3 per week but not required.

Weigh-ins: Yes, plus body measurements.

Background: A team of registered dietitians and an impressive medical advisory board.

Commitment: None, other than prepayment. Can cancel with a full refund.

Upshot: Emerging as a leader in the area of packaged food and weight loss.

TOPS CLUB (TAKE OFF POUNDS SENSIBLY)

(414) 482-4620, www.tops.org

Members: 200,000.

Locations: About 10,000 chapters.

Dieting style/method: The nonprofit TOPS Club supports members with weekly meetings at chapters throughout the U.S. and Canada. They use private weigh-ins, positive reinforcement and professionally prepared programs, featuring information on nutrition, exercise and healthy lifestyles. Questions are answered at TOPS centers, by phone and e-mail.

Best fit: Budget-minded, work well in groups.

Exercise: Yes.

Staff: 423 area captains, 128 coordinators and 12 regional directors assist skilled volunteer chapter leaders.

Cost: $24 annually ($30 in Canada) plus chapter dues of 50 cents to $5.

Supplements: No.

Weigh-ins: Yes.

Background: Founded in 1948 by Milwaukee homemaker Esther Manz.

Commitment: No contract.

Upshot: Friendly, encouraging and a not-for-profit.

L A WEIGHT LOSS

(800) 526-7546, www.laweightloss.com

Members: 150,000.

Locations: 900 worldwide.

Dieting style/method: One-on-one counseling with customized meal plans. Coaches focus on three-tiered approach — weight loss, six-week stabilization phase and maintenance. No food is sold.

Best fit: Need personal coaching, and those who have the time to investigate their local center.

Exercise: Yes. Part of a customized program.

Staff: Counselors made up of former or existing customers, who receive additional training.

Cost: From $7-9 per week (based on a minimum 52-week program).

Supplements: Yes, they sell supplements and bars, but they are not required at all locations. The cost varies but is approximately $4 per day.

Weigh-ins: Yes.

Background: Backed by weight-loss pioneer Harold Katz and supervised by registered dietitians and a medical director.

Commitment: Yes, varies by franchise. You pay in advance, so make sure you understand the commitment and the counselor availability first.

Upshot: The company message seems inconsistent. Make sure to get pricing in advance. If you can't obtain this information over the phone, don't waste your time.

ZONE DIET AT HOME

(800) 343-8036, www.ZoneDietAtHome.com

Members: 2,500.

Locations: Online or by phone

Dieting style/method: Convenience, prepared foods. The meals, which are delivered to your home, are made up of 40 percent carbohydrates, 30 percent fat and 30 percent protein. Options: Lifestyle Program (fresh meals); Optimum Results Program (frozen meals); FroZone (gourmet frozen meals); and Kosher FroZone (gourmet, kosher frozen meals).

Best fit: The busy, particular eater who doesn't cook.

Exercise: No.

Staff: One nutritionist.

Cost: $24.99 per day to $41.99 per day (depending on program choice) plus shipping (about $40-$50 per week).

Supplements: Available, but not required.

Weigh-ins: No.

Background: Accredited and experienced chefs, together with a nutritionist and food stylist, develop the meal programs.

Commitment: You can cancel at any time, but the company will not take back food.

Upshot: Flexible, balanced food options.

Charles Stuart Platkin is a nutrition and public-health advocate, and author of "Breaking the FAT Pattern" (Plume, 2006). Sign up for the free Diet Detective newsletter at www.dietdetective.com.