When my dad was a 12-year-old kid in Red Bluff, California, circa 1928, part of the extended family was a man he knew as Uncle Jack Cotney. That they knew of, or he'd admit to, Uncle Jack had survived some 25 stand-up gunfights in his life.
Green tea is a fat burner that does speed up the metabolism, as far as energy drinks however they really speed up the heart not your metabolism. If you're looking for something that will speed up your metabolism there are better choices for that. Good Luck, Casey.
Grapefruit enzymes reduce the amount of insulin that the body makes which helps the metabolism stay regulated. A well-regulated metabolism helps you to lose weight faster and more effectively. Scientists do acknowledge that grapefruit has properties that balance out blood sugar levels and help the metabolism.