The potential use of meal replacements to assist in weight management has been examined in several studies. Meal replacements can include shakes, powders, or bars that replace a normal meal. They are easy to use, require little if any preparation, and most important they provide structure to the daily eating plan. It is estimated that as many as 15% of adults are using meal replacements as a strategy for losing weight. In the longest study to date (5 years) overweight subjects who consumed a meal replacement shake lost weight (about 10 pounds) compared to a group of control subjects who gained about 15 pounds over the same period. Other controlled studies of shorter duration have shown that meal replacements can assist in weight loss. The value of meal replacements is that it changes behavior, and for some people the structure of having a prepared meal provides the needed motivation to reduce calories and enhance weight loss.

Keogh JB, Clifton PM. The role of meal replacements in obesity treatment. Obes Rev. 2005 Aug;6(3):229-34.