SOY VS. WHEY
According to eHow protein powders usually have one or a combination of the following proteins: egg, whey, soy, and rice. Of the four, soy is the most complete while whey is the most common. Whey protein is a low-fat byproduct of cheese made from milk, it also helps muscles recover after workouts (important for athletes and body builders). Soy protein is obviously derived from soy flour. Compared to whey, soy protein is lower in calories and saturated fat and a great alternative for strict vegetarians. In my personal opinion, both are good and I don't really think you will lose going either way. If you want it all, they do sell the powders with both (i.e. see above picture).
Now you can use protein shakes as a meal substitute, which can be an obvious way to lose weight. However, when you do that I suggest you do your research. Some products will try to suggest that the shake alone will make you lose weight. In reality, it is often the fact that you are reducing your meal portions as well your intake of calories and fat. But when you do that you won't get all of the needed nutrients you would get in a well, balanced meal. Don't get me wrong, I've tried my share of liquid substitutions. But I feel as though you have to know what is in the substance you are drinking. Check out if the sodium is high or the sugar. Just because the calories are low or the fat, doesn't mean it is really doing anything for you in the long run.
I personally use protein shakes to help me maintain the muscle from my work outs and to help repair my body as well. However, what you mix with you shake makes a difference as well. You can use milk or water to make your shake. I have used both and you can definitely tell the difference between the two. Obviously water won't add to your calorie intake, but it doesn't taste as good. I prefer to use milk. I use 1% skim milk, which alone is nasty, but with it you get calcium and avoid most of the fat you get with whole or even 2% milk.
Also, I suggest a blender to mix your shakes. While many advertise that the powder is easily mixed with any beverage by simply shaking it in a container, I often find it comes out chunkier than I would like. The blender is going to give you a smoother taste and texture
Now moving on from the obvious.....
So if you haven't tried protein powder during your weightloss journey, give it a try. So far I have lost an inch off of my waist and hips in the last two weeks! Progress, progress, progress:-)
For some more information on soy and whey protein, check out the following sites: