Caffeine in Diets

"The Boston Globe" reports that adolescents that drink more caffeine may be more likely to feel tired in the morning and have difficulty sleeping. Poor sleep quality and caffeinated beverages may also be associated with weight problems like childhood obesity. High caffeine consumption may impair concentration and cause restlessness that diminishes performance in school.

Stimulant

Caffeine belongs to a group of drugs called xanthines and it is the only xanthine that is used regularly as a central nervous system stimulant. According to the University of Utah College of Pharmacy, caffeine is the mostly widely used psychoactive medication in the United States. The U.S. Food and Drug Administration classifies caffeine as the only safe and effective stimulant for over-the-counter products. Stimulants like caffeine increase nervous system activity. Caffeine can provide more energy and reduce your perception of fatigue.

Sensitivity

The University of Utah College of Pharmacy suggests that the stimulant effects of caffeine are most dramatic for people that are tired or bored. Stimulant users may like the effects of caffeine and become dependent on them. According to MayoClinic.com, your reaction to caffeine may depend on the amount of caffeine that you are accustomed to consuming. You may have more sensitivity to caffeine if you do not consume it very often and you may also be more susceptible to the negative effects of caffeine. For example, you may experience anxiety or sleep problems from a single serving of caffeinated coffee if you are not used to consuming caffeine.

Metabolism

Your body absorbs and distributes caffeine very quickly and passes the stimulant onto your brain. Caffeine enters your bloodstream through your stomach and small intestine. Your blood or body tissue does not store caffeine and you excrete the substance in your urine several hours after consuming it. According to the University of Washington, your body may take six hours to eliminate just half of the caffeine that you consume with a particular dose or serving. However, you may experience the stimulant effects of caffeine as soon as 15 minutes after consuming it.

Weight Loss

According to MayoClinic.com, caffeine may slightly boost weight loss or prevent weight gain, but these effects may not be significant or permanent. Caffeine may temporarily suppress your appetite. Caffeine increases the amount of urine that you excrete because it is a diuretic; this may temporarily reduce your body weight by reducing the amount of fluids in your body.

Side Effects

According to MedlinePlus, caffeine may produce negative side effects associated with excessive consumption or abrupt withdrawal. High consumption of caffeine may cause nausea and vomiting in addition to anxiety or depression. You may experience tremors or difficulty sleeping and restlessness if you consume too much caffeine. Withdrawal symptoms that are associated with caffeine include headaches, drowsiness and irritability. MedlinePlus recommends gradually reducing your intake of caffeine to avoid symptoms of withdrawal.