If you're looking for a high quality weight gain drink, packed with whey protein and the healthy calories you need to bulk up and add size, you'll love Maximuscle's Progain The weight gain product, Progain, offers you a special whey protein and complex carbohydrate blend, including the special low Glycemic Oligofructose (nutriose) and inulin slow release carbohydrates, giving you a combination of fast nutrient uptake and sustained energy release with an easy to digest, but energy dense 453 calories per serving.