By Erica Lesperance, RD, LD

If you stay up late enough watching television, you are bound to see countless offers you "can't afford to pass up" on products such as the perfect all-purpose food chopper, lotions that eliminate cellulite, and of course, abdominal machines that promise you that 6-pack you've always dreamed of but never before could attain. Celebrities and infomercial stars with rock-hard abs swear that they achieved fitness through one ab machine or another. Could this be true? How do you know if you should call that toll-free number? The Diet Channel condenses the American Council on Exercise (ACE) and Consumer Reports magazine's investigation of the effectiveness (or ineffectiveness) of some of the most popular ab machines sold on television today.

Body Dome

The Body Dome looks like an inflatable exercise ball cut in half with a rubber base and elastic cords attached for strength training. For $140, the makers of the Body Dome claim that you will look great naked and burn off as much as a pound a day by using the dome for aerobic exercise, strength training, and ab conditioning. While weight loss can be achieved through using the Body Dome's cardio video, the pound per day claim is, at best, highly unrealistic and, at worst, a complete lie. Weight loss can be achieved through many forms of aerobic activity, and is not dependent on the use of the Body Dome. As for ab conditioning, Consumer Reports finds the Body Dome "provides balance training and targets core trunk muscles" like an exercise ball, but a ball is cheaper. Bottom line: Don't waste your money.

Ab Swing

For $115, the makers of the Ab Swing claim that this contraption, a padded bench that rocks on a metal base, will sculpt your lower abs, upper abs, and obliques while you "sit and swing" for less than 5 minutes a day. However, a San Diego study that tested the Ab Swing, along with five other home abdominal machines, found that this machine was "significantly less effective than a crunch at eliciting upper and lower rectus abdominis activity." Bottom line: Do crunches - they're free and more effective.

Smart Abs

For $93, you can purchase Smart Abs, which is a padded frame that you hold in your lap. You rock forward into the resistance. The creators of Smart Abs claim that regular crunches do not work your abs or obliques because you lift 1/3 of your body weight using unnecessary muscles. While it is true that the standard crunch is not the most effective abdominal strengthening exercise, it is more effective than Smart Abs. Due to your upright position when performing the Smart Abs exercise, you lose the benefits of lifting your own upper body. Nonetheless, the makers of Smart Abs claim you'll flatten your stomach, sculpt your waistline, eliminate love handles, and lose 10 pounds and 2 inches in 2 weeks. Not only is this an ineffective way to strengthen your abdominal muscles, it is highly unlikely for major weight loss to occur without significant aerobic activity and a healthy diet. No matter what the exercise or machine, 2 minutes per day is not enough to produce the type of results the makers of this machine are claiming. Bottom line: Is this a joke?

AB-DOer

The Ab-Doer is one of the most recent infomercial crazes evaluated by ACE. It looks like a chair with a padded seat and shoulder-height handlebars. To use the AB-Doer, you grip the handlebars and rotate the torso in various directions at various speeds to strengthen muscles and elevate heart rate. The claim is that you aerobically burn fat at the same time you flatten your stomach in just minutes a day. However, a study out of California State University, Northridge, found that over all, the AB-Doer provides a relatively low-intensity workout that burns approximately 4 to 5 calories per minute. By comparison, walking on a treadmill at three miles per hour (which is the equivalent of a light-to-moderate walk) burns approximately 5.3 calories per minute. In terms of strengthening muscle, the study found AB-Doer also falls short in this area, as the exercises elicited less activity than most traditional abdominal exercises. Bottom line: Save your $109.

Other infomercial ab machines

Similar stories exist for all the infomercial abdominal exercise machines, including the Ab Rocker, Torso Track, Ab Roller, Ab Works, and ABSculptor. According to Richard Cotton, the editor of ACE Fitness Matters, "These devices provide no apparent benefit or detriment when compared to a properly performed crunch." However," Cotton says, "if any of these devices serves to motivate an individual to begin and continue an exercise program, then they would seem to have a benefit." Just be aware that none of them live up to their outrageous claims.

Guaranteed toned abs

So what should you do to tone your abs and make them visible? Lose any excess fat around your midsection so your abdominal muscles show. Working your abs will not burn fat in that area. Rather, you must step up the aerobic exercise and eat a healthy, well-balanced diet, so you burn off more calories than you take in. Find a few abdominal exercises that you can commit to doing several times per week. Whether or not you use an ab machine, include some exercises that have been proven most effective. According to the San Diego State University/ACE Abdominal Study , the top 4 exercises for overall strengthening of your abs are the bicycle maneuver, the captain's chair, crunches on a fitness ball, and reverse crunches.

The money you would have spent on an expensive ab machine might be put to better use on a $30 fitness ball and a session with a personal trainer to help you perfect your form and make the most of your workout.

For more information on abs exercises see the following article from TheDietChannel: Ab Exercises: General Info and Ab Exercises: How to Get Great Abs.