Green tea has been used for centuries due to its health benefits like sickness prevention and stress relief, but it's also great for our metabolism. Green tea is rich in substances like antioxidants called catechins and caffeine, which can increase metabolism when they work together. "They help to boost levels of the hormone, norepinephrine, which signals for stored fat to be released into the bloodstream so that it can be used as energy," Lee told POPSUGAR. However, not all green teas are made equal, so it's important to research companies and brands. Additionally, "the amount of catechins in a cup of green tea varies depending on the precise type of tea, the ratio of tea to water, and how long it is left to infuse," according to Lee.