A bodybuilder relying on multiple shakes per day in place of whole food will have a very different physique from one who eats more whole food. The natural digestion process is important and you can only get that with whole foods. Protein powders are broken down so much that they do not digest and get absorbed like food. It is better to add specific amino acid supplements to a meal than to replace a meal with a shake. However, we do not live in a perfect world and because of work or family obligations we may end up missing meals. In such situations, shakes can be used. But when you are dieting, would you rather have a protein shake made with water or a grilled chicken breast and sweet potato?