Weight Gain Shakes are most popular with athletes but can be used by anyone looking to increase their lean body mass; seniors, those with high metabolic needs, those recovering from long term illnesses are all good candidates to use weight gain shakes, too. Weight gain shakes conveniently provide substantial amounts of proteins, carbohydrates, fat and calories, but in precise ratios that favor full utilization of these nutrients for positive growth and anabolic effects, instead of merely increasing bodyfat storage.