Coffee does not have the role of weight loss, weight loss coffee if excessive drinking will affect the quality of sleep, calcium deficiency and other phenomena. 1. Impact on sleep quality: In diet coffee, containing caffeine and alkaloid substances, will cause some stimulation of the cerebral cortex, a large number of drinking easy to cause excitement, restlessness and other symptoms, if too much to drink, will have an impact on the quality of sleep, and may even cause insomnia or aggravate insomnia. 2. Calcium deficiency: caffeine in coffee diuretic, will increase the loss of calcium from the urine, excessive drinking diet coffee will lead to the loss of calcium in the body, resulting in a lack of calcium in the body. Weight loss needs to control the mouth, open legs, can not rely on a certain food or health care products to lose weight.