If drinking a cup of coffee makes a person feel tired, the effects of caffeine may be responsible.
Caffeine increases alertness by inhibiting certain chemical processes in the brain that regulate the sleep-wake cycle. However, once the body completely metabolizes caffeine, it can make people feel tired as the body will look to recoupe the deficite.
The rate at which a person’s body metabolizes caffeine varies depending on genetic and lifestyle factors.
People who drink coffee every day may develop a tolerance to caffeine’s stimulant effects, which means that they need to drink more of it if they want to experience similar results.