OPTIFAST shakes are nutritious shakes offered as part of the OPTIFAST diet program. When following the OPTIFAST diet program, dieters will consume five shakes each day. Each shake contains 160 calories, as well as one-fifth of the recommended daily serving of vitamins and minerals. When drinking five shakes a day, dieters are expected to lose anywhere from seven to 14 pounds in the first week and three to seven pounds each following week. While OPTIFAST limits dieters to 800 calories a day, these shakes are formulated with the perfect amount of vitamins and minerals to keep you healthy, while helping you lose weight.