Carnitine is a small molecule involved in building skeletal muscle. Greater muscle mass results in greater use of fats for energy at rest and during exercise. Caffeine promotes the release of fat from fat cells to be used for energy. Take them together and you’ve got a more effective recipe for enhancing exercise endurance (and, perhaps, fat loss) than taking either alone or neither.
Research agrees; studies have indicated that taking carnitine with caffeine may boost endurance by increasing fat release into the bloodstream and fat usage by active muscles, thus providing the body with a sustained fuel source during prolonged exercise bouts.
Take 1 to 1.5 grams of L-carnitine or acetyl-L-carnitine and 200 milligrams of caffeine 30 to 60 minutes before workouts.