Protein shakes and powders can cause weight gain depending on the person's activity level, overall calories consumed and the nutritional content of the protein shake. Some protein shakes contain fats and carbohydrates that add excess calories, while others are almost 100 percent protein.
The type of protein in the shake affects how well the body absorbs and uses it. Most protein powders are manufactured from soybeans; dairy products, such as milk, whey and casein; eggs; or rice.
Most adults need to consume 45 to 56 grams of protein every day. Athletes and physically active people may need more than this to help repair muscles that are taxed during workouts. The body can process between 5 and 9 grams per hour, and since many protein shakes have 40 grams of protein per serving, it is easy to consume too much.
Protein creates a feeling of fullness, so protein shakes may help with a short-term weight loss plan, and the protein also aids in building muscle tissue; however, protein that isn't used to build or repair muscle tissue gets converted to fat or waste by the kidneys. This process is hard on the kidneys and also requires calcium, which is extracted from bone tissue.