I recommended the VitaMix. I bought one last June. I use it to mix protein smoothies and veggie/fruit smoothies. I have a protein drink for breakfast 3 or 4 days a week (low fat yogurt or 1% milk, protein powder, berries). I drink a veggie smoothie in the afternoon or evening in place of snacks. Without changing anything else (I eat a healthy diet, but do eat carbs, drink wine, exercise moderately). I have lost 12 pounds in 6 months. If you use it to consistently replace one meal a day with a nutritious drink made with protein powder you might get much better results.
I use Jay Robb protein whey powder. No carbs, no fat, 25 grams of protein.
Which Vitamix model? There are so many.
My vitamix is a Creations II 48 oz 12 in 1 variable speed. It was the least expensive. I really wanted one for smoothies and making soups. There are lots of models, this one fits under the kitchen cabinets. Many of the models are too tall for that. I got it on QVC on a whim. I love it and use it often.