The key to weight loss is filling up on low-cal foods that are high in fiber to keep you satiated longer. Flaxseeds contain both soluble and insoluble fiber, and when ground into flaxseed meal and added to a smoothie, you'll hardly taste it. As a bonus, flax also offers essential omega-3 fatty acids. Try this pumpkin protein smoothie that offers over 11 grams of fiber.
Leslie said you can also add chia seeds, which are also a great source of healthy fats and fiber to keep you satiated. Try this strawberry protein smoothie that includes cottage cheese for the protein source.