Clark added that even though THC may cause an initial spike in appetite, the metabolism boosts more than makes up for it over time. He continues by assuming that the consequences of lowering obesity would be even higher if current strains had lost the munchie effects but retained increased metabolic rates. And you don’t have to be a heavy smoker to lose weight. According to research, using marijuana just once can increase your metabolism for approximately four weeks, making you appear substantially leaner.