This low calorie smoothie contains green tea, which stimulates fat loss via substances called catechins, while lowering cholesterol. At 46 calories per serving, you will burn more calories digesting this smoothie than you will absorb from it. The apple mellows the spicy flavor of the watercress while the mint enhances the green tea tanginess. Try our green tea weight loss smoothie recipe as an appetizer or a pre-workout thirst quencher. Check out this exhaustive list of greatness in this smoothie: it is a good source of calcium, manganese, magnesium, potassium and vitamin B6. It is an excellent source of fiber, vitamin A and vitamin C.