The promise: Work out harder and rev your metabolism for longer when you caffeinate pre-workout.
The proof: Good news for coffee lovers who want to get in shape. Studies show that caffeine not only helps you work out stronger and longer, but also boosts your metabolism by 15 percent for as long as three hours after you stop exercising.
“Caffeine is good for exercise because it increases energy and alertness,” says Kirkpatrick. Plus, if you tend to metabolize substances slowly, caffeine might help you work harder during exercise session, she adds. “The harder you workout, the more your metabolism is increased afterwards.”
To reap the exercise benefits, ingest 3-9 mg of caffeine per kilogram (kg) of body weight (which translates to 1-2 cups on the lower end and 5 to 6 cups on the higher end) one hour before working out, according to the American College of Sports Medicine.