I'd hold off on protein powder shakes until you're comfortable with your weight. I think those would be better to take after a ride when the goal is to repair/build muscle. I'm pretty trim, but when i started riding more than an hour, especially over 1.5 hours, thats when I had a noticable increase in appetite. I'm thinking that if weight loss is your goal right now, try increasing the time you spend riding.
For shakes, I've tried: frozen fruit w/ milk and/or yogurt; 2 cups milk + 1 or 2 bananas + a bit of honey; and probably my favorite, 2 cups chocolate milk + bananas, sometimes with peanut butter added.