There isn't necessarily a certain protein source that is better or worse for losing weight. All protein sources contain the same amount of calories, so you can't really say one helps you lose total weight more than another. They all contribute 4 calories per gram to your diet.
However that doesn't mean all protein is created equally. We suggest focusing on quality and complete sources of protein. You get more "bang for your buck", where your body can utilize the protein better for things that protein is good for - controlling hunger, repairing muscles, supporting metabolism, etc.
Casein protein is a very high quality protein source, complete in all essential amino acids. It is also a slow digesting protein. In that sense you could say that it's good for weight loss because it can help keep you fuller longer. If it helps with reducing portion sizes elsewhere, then it's definitely a benefit to your weight loss! (along with the other benefits of consuming quality protein).
- Matthew Mazzino, Registered Dietitian