You may want to add a little 'good' fat, like flax-seed oil. It will help the shake 'hold' you longer. I didn't like the taste at first, so started with a tiny bit and gradually added more.
Please be very careful with the soy as it can cause thyroid problems, among other things. If you're using it, please keep a close check on your thyroid function - like every month. Here is a small extract of a piece written by a nutritionist:
"Taking 40mg of isoflavones ... I tried the experiment on myself and developed full blown hypothyroidism in
10 days."
Here are a couple of links with heaps of info on why not to use it:
http://www.soyonlineservice.co.nz/ http://www.mercola.com/article/soy/
As an approximate guide 30 mg of soy isoflavones can be found in:
Soybeans and soyflours: 9 - 20g (0.3 - 0.7oz).
Soy mince: 12g (0.4oz).
Tofu: 50 - 110g (1.8 - 3.9oz).
Soy milks: 150 - 240g (5.3 - 8.5oz).
Miso: 35 - 45g (1.2 - 1.6oz).
Soybean sprouts: 80g (2.8oz).