Fact: One study compared those who took casein to two other groups. One consumed whey protein and the other had no protein. The researchers found that the casein group experienced double the muscle growth and triple the fat loss compared to the placebo group. The casein group also experienced more fat loss than the whey group.
In one study, a casein protein shake before bedtime helped strength-training men increase type 2 muscle fiber size by 8.4 cm2 in the supplement group, compared to 4.8 cm2 in the training-only group. They also found the casein group increased strength to a greater extent, or about 20% more than the training-only group. Much like whey, casein has been repeatedly shown to increase muscle growth and strength when combined with resistance training. It may also help with fat loss.