Slim-fast

The meal replacement plan has evolved over the years and now offers nutrition bars, meal bars, smoothies, snacks and powders. SlimFast boasts that there are more than 30 clinical studies that reveal the effectiveness of the weight-loss program.

In addition to the diet-friendly, convenient products offered by Slim-Fast, the company also puts forth personalized meal plans known as Slim-Fast Optima -- a nutritious balance of protein, healthy fats and complex carbohydrates. There are also lower-carb, low-sugar products for the carb-conscious dieter.

Women consume an average of 1,200 calories per day on the Slim-Fast plan. Maintaining this calorie level promotes weight loss. So that dieters get a wide variety of foods, the meal plan integrates both Slim-Fast products and nutrient-rich whole foods. According to Slim-Fast, their program provides 100 percent of the essential nutrients your body needs.

There's also the convenience factor. For the dieter who's always on the go, being able to grab a meal replacement shake or bar and a piece of fruit is a dream come true.