There is absolutely NO reason, for you to be on a protein shake diet. This is a very EXTREME thing, and the only reason that it is being prescribed for your husband is because of his impending gastric bypass surgery. Basically, the risks to his health because of his extreme weight are outweighing the risks of the diet for him at this point.
You should not be eating only 3 protein shakes a day, and no other food, especially since you are currently NOT under a doctor's care for obesity. Please, continue to do your calorie counting in the way that you have been doing.
Also, the Slim-Fast plan is NOT 3 shakes per day and nothing else. It is a shake for breakfast and lunch, and then you eat a real dinner, and have snacks as well-fruits, etc. It isn't only 3 shakes a day. It is not the same as what the dietician is prescribing for your husband.
As far as your husband is concerned, do not use Slim-Fast products for this 3 shake a day. They are not what is being prescribed for him to do. You want to make the shakes with actual protein powder.
Now, my husband tried the GNC protein powder, and he HATED it. (My husband bodybuilds, and uses it as a dietary supplement for that.)
He likes the ON brand of protein powder, and it is also sold at GNC. I *believe* it is in a black container. He likes the double rich chocolate flavor. I like Designer Whey brand protein myself.
Please note that this is a dietary supplement, so your husband should not expect it to taste like a milkshake.
I prefer them mixed in the blender, with a couple of ice cubes added. My husband just mixes them in his shaker container.
Please, your husband is under the advice of a physician due to his upcoming weight loss surgery-you are not. Please don't do this extreme thing along with him.