No, according to Health. com, the weight loss effect of L-carnitine coffee is not reliable. Because L-carnitine is a slimming product, although it can play a certain slimming effect after taking it, long-term use will do harm to the body, easily increase the burden on the kidneys and easily cause irregular menstruation. In severe cases, it will also affect the normal reproductive function, and there will be a serious rebound after stopping the drug. The best way is to lose weight through aerobic exercise and diet control, which requires long-term persistence.