'Crash' diets are eating plans designed to provide quick weight loss by drastically cutting calories. However, such diets may be lacking in proper nutrition, especially those that focus on a single food or food group.

Two of the most common types of dieting gimmicks are pills that profess to help you burn fat effortlessly and creams or body wraps that supposedly 'melt fat away.

A food exchange program is a diet in which foods are organized into several groups, such as proteins, fats, fruits and vegetables, dairy products, and grains.

High protein diets have come in and out of fashion since the late 1960's, each time under different names or with slightly different guidelines. However, the basic premise remains the same: these diets claim that carbohydrates make you fat by triggering the release of too much insulin, among other effects.

Liquid diets range from over-the-counter shakes that you substitute for a meal to medically-supervised fasts in which only liquids are allowed. For those with just a few pounds to lose, meal-replacement shakes can be a safe and effective way to take off weight, assuming the product includes a wide range of nutrients.

A low-fat diet can be an effective way to lose weight and improve your health. In addition to reducing your risk for heart disease, cutting back on fat can enhance weight loss in several ways.

The 'Rotation Diet,' known more recently as the 'T-factor 2000' diet, is designed to be a long-term system for losing weight and keeping it off. Its main focus is on low-fat, high- carbohydrate eating, with few processed foods.

It seems practically every week, a new diet craze is being launched. Some advocate eating only those foods that your ancestors could have hunted or gathered, as in the Paleolithic (pail-ee-oh- LITH-ick) or 'cave man'-type diets.